Current concepts In the Management of oral cancer

Current concepts In the Management of oral cancer
A short scientific communication by Dr. Rehan A. Kazi M.S. (ENT), Fc.Oncology
Dept. of Oncology, Masina Hospital, Bombay, India.

Introduction:
Malignant disease in and about the oral cavity has its origins from a variety of tissues. It may represent a primary neoplasm of local tissues or deposits of disseminating lesions from other parts of the body. Squamous cell carcinomas, together with salivary gland neoplasm, from the major proportion of malignant neoplasm are encountered in the oral region. Malignant melanomas are rare in the oral cavity but assume some importance owing to their aggressive nature and the consequent poor survival rate. Metastatic deposits usually arise from primary neoplasm of the breast, kidney, lung, prostate, and gastrointestinal tract.

The involvement of teams of health workers in the care of patients suffering from oral cancer is rightly assuming greater prominence. The blind goal of curing the cancer should not be allowed to obscure the importance of the quality of the patient's life. Social workers, physiotherapists, speech pathologists, dietitians, and nursing staff can all contribute to a balanced view of the patient's treatment requirements. The course of treatment prescribed should never fail to be in harmony with the patient's wishes.

The care of a patient who presents with oral malignancy has several phases. First, a diagnosis of the type and also the extent of the disease must be made. The active phase of treatment can then be planned and proceed. Following treatment, attention must be given to rehabilitation of the patient and early diagnosis of recurrence or a second neoplasm.

The chance of curing a patient suffering from oral carcinoma is related to the stage of disease progression at the time of diagnosis. Langdon et al. (1977) found that 5-year survival of their patients was obtained in 51 percent of cases suffering from stage-1 diseases. Only 8.3 percent of those with stage-IV disease survived for this time. Other studies confirm the expectation that disseminated oral carcinoma carries a very bleak prognosis. Early detection is obviously of paramount importance. Both the patient and the clinician can contribute to this aim. Therefore, it is important to draw people's attention to the necessity of having any chronic abnormality in the mouth investigated. Dental practitioners, medical practitioners, and allied health personnel should remain alert to the possibility of finding oral cancers.

Principles of diagnosis:
Clinical examination: The emphasis for the dentist should be on an oral examination of each patient rather than a dental examination. This should include the accessible oral tissues and indirect examination the nasopharynx and larynx. Persistent white patches, red patches, ulcers, lumps, loose teeth, and radiographic abnormalities all require investigation. Palpation of the neck should be omitted. Cervical lymphadenopathy may indicate malignant disease and should always be further investigated.

Biopsy: No treatment of lesion should proceed before histologist confirmation of the lesion's malignancy is available. Every cases of clinically obvious malignant lesions, the tissue of oral may not be as expected. The degree of differentiation also not to be established. Both of these factors will influence a prognosis and treatment strategy.

If practicable, the clinician who is to treat the patient should be given the opportunity to perform the biopsy. This allows him to assess the lesion before any surgical mutilation. The experienced clinician is also best able to select appropriate site from which to sample the tissue. The biopsy specimen should include the pathological lesion with a many of normal tissue. Areas of necrosis must be avoided, as it may not be diagnostic. It must also be of sufficient adeptly reveal any invasion of deeper tissues. In areas of miss-appearance the sampling of tissue from more than one site necessary to minimize the chance of a false negative report.

An excisional biopsy should not be attempted. On carcinomas are often found to be deeply infiltrating and attempt at excision biopsy will often fail and, more of provide inadequate margins of clear tissue. Subsequent surgery treatment can be difficult, as the area has been mutilated.

Manipulation and instrumentation of the area also to be avoided and this principle continues to apply until tumor is removed. Most oral lesions are sufficiently access to allow biopsy while the patient is conscious. Top anesthesia may be adequate in some cases or nerve blocks be employed. In filtration adjacent to the lesion should be avoided. For masses in deeper tissues or less accessible areas, general anaesthetic provides an opportunity to perform the biopsy and for a good clinical assessment of the lesion. The tissues are gently palpated to gauge the extent of infiltration present and the involvement of adjacent structures.

Cytology: In the 1960s the National Cancer Institute of the USA sponsored several field trials designed to test the value of cytological screening for oral cancer. This was in response to the success of 'PAP' smearing for cervical cancer as the oral cavity was seen as an analogous site. False negative results commonly occurred and positive smears required confirmation by incisional biopsy. This diagnostic procedure has now been largely abandoned.

Fine needle aspiration: Fine needle aspiration cytology has found an increasing role in the diagnosis of head and neck malignancy. The technique finds particular application for the diagnosis of deeply situated masses, in the confirmation of tumor in suspiciously enlarged neck nodes, and in the assessment of areas of possible recurrent diseases. The technique is attractive as it is reliable and inexpensive. It is also well tolerated by patients. A needle is passed into the target mass and cells are aspirated. The success of this method depends on the accuracy of needle placement and the reliability of the diagnosis, on the skill and experience of the tissue pathologist. Where these are of a high standard results are good. The diagnosis of salivary gland malignancies using needle aspiration was shown by Frable and Frable (1982) to be 92 percent accurate for the presence of tumor and 99 percent correct for the absence of malignant cells.

The possibility of tumor cell seeding via the needle tract has received wide investigation. In a search of the literature, Frable and Frable (1982) found no confirmed cases of tumor dissemination following this technique and experimental evidence is in agreement that such an occurrence is unlikely (Berg and Robbins 1962; Engzell et al. 1971).

Principles of patient assessment:
General assessment: Following histological confirmation of the presence of an oral cancer, each patient should undergo a thorough assessment. This serves two important purposes. First, the extent of the malignant disease is accurately delineated and also the fitness of the patient to undergo treatment is determined. Many patients afflicted by this disease are elderly. Not only are such patients likely to be suffering from other chronic illness, they are also at risk of having malignant disease of the respiratory of digestive tract. These may be coincidental or may arise in the future. Synchronous carcinoma of the head and neck, lung, and oesophagus may arise as frequently as in 10 percent of cases. As a reaction to this fact, panendoscopy of these areas has been recommended by Atkinson et al (1982) as a standard investigation.

Anorexia and weight loss are ominous signs of most cancers but painful lesions of the oral cavity may interfere with normal diet and this may account for the weight loss. If the disease becomes widespread cachexia may be seen. Cardio-vascular or respiratory disease reduces the patient's tolerance of stressful treatment. However, modern anesthetics and intensive care have been refined to the degree that few patients need to be refused a general anaesthetic. Kidney disease is of particular relevance to chemotherapy as some agents are excreted or metabolized in the kidney. Routine investigations include physical examination, chest radiograph, electrocardiogram, creatinine clearance, and blood chemistry.

Local assessment: The oral lesion is carefully examined and details recorded. Photography is of great value in assessing the response of the lesion to treatment. The degree of involvement of adjacent structures by the tumor can be assessed by palpation. Areas of paraesthesia, nerve palsy, and fixation of tissues provide further evidence of the involvement of regional structures. The presence and extent of bone invasion must be accurately determined. This dictates the necessity for an extent of jaw resection and influences the planning of radiotherapy. An orthopantomogram provides a good screening view of the jaws. Antral radiographs are of value for showing the extent of some maxillary tumors. Intra oral radiographs such as occlusal and periapical views are often of great value as they can provide detail of the bony cortex in specific areas. Massive bone invasion can be detected on these radiographs but early and more superficial infiltration is more difficult to detect. Details of the site and extension of deeply situated and inaccessible lesions can be provided by CT scanning. CT technology has rapidly developed over the past decade and modern scans provide images of great diagnostic quality. However, the most sensitive indicator of tumor involvement is still the clinical assessment, which relies both on examination and palpation of the lesion, as well as noting symptoms such as pain or nerve sensibility changes (Leipzig 1985).

Where investigations lead to the suspicion of a metastatic lesion, either to or from the oral region, confirmation is required. Plain radiographic views, chest or abdominal CT scanning, ultrasound, or radio nucleotide scans can be used to identify metastases. The technetium bone scan is a useful screen for bony metastases. False positive results owing to chronic disease or traumatic lesions are common, but can be excluded by reference to the history or by plain radiographic views.

Clinical staging: The staging of malignant disease can be accomplished by various systems. The most valuable of these provide some indication of the prognosis for the patient and can be used as a guide to appropriate treatment. A number of systems for categorizing oral cancers have been proposed. All recognize the importance of the size of the primary tumor, the extent of any regional lymph node involvement, and the presence of metastases. The contribution that site of the lesion and histological type have on the chance of survival of the patient is recognized by the STNMP system, introduced by Rapidis et al (1977). Four stages are recognized by this system ranging from stage-I, which describes localized disease to stage-IV, which carries the gravest prognosis. In comporting their classification with that of the TNM system in 131 cases of oral carcinoma, Rapidis et al. (1977) found that their system gave a more precise correction with the outcome of the disease. Both Europe and America offer TNM systems. Perhaps the most widely used is from the international Union Against Cancer (UICC 1987; No classification has been universally embraced. This presents some difficulties in the comparison of data coming from different clinics or countries. Unfortunately, standardization of classification does not appear to be imminent.

The development of current treatment strategy:
Vikram et al. (1984a,b,c) reported on the patterns of treatment failure in their patients with stage-III and IV head and neck carcinoma. The treatment was based on surgery and postoperative radiotherapy. Only 5.6 percent of patients developed a local recurrence within 2 years of treatment. This success confirms the impression that, if the resection provides histologically clear margins and radiotherapy follows, the likelihood of recurrence of the primary is minimal. Of those patients who were surgically treated for confirmed cervical metastases, 5.7 percent developed a recurrence in the neck. This statistic contrasted with that from a previous study from the same clinic (Strong 969) where, in a sample of patients treated by surgery alone, 36 percent had recurrence in the neck. The authors found that distant metastases from head and neck cancers assumed greater importance as better local control was achieved. The improvement in survival expected to occur following the combination of surgery and radiotherapy has been partly offset by failure to control the cancer spread below the clavicles. Follow up of the patients over the ensuing 5 years also revealed that 17 percent developed second malignancies. This is a high and disturbing figure (Vikram et al., 984d).

Data such as these serve to indicate some of the directions our treatment strategies should take. Early diagnosis remains of utmost importance, as tumors with local involvement are the most easily cured. The combination of radiotherapy and surgery is capable of eradicating disease above the clavicles in the majority of cases. Prevention of the occurrence of distant metastases is presently being addressed by the use of chemotherapy.

In the treatment of advanced cancer, surgery generally follows induction chemotherapy, with radiotherapy administered to the primary site and neck after initial healing of the surgical site.

The need to treat the disease with multiple therapies will depend on factors such as the degree of histological differentiation of the lesion, the site, size and stage of the malignant mass, and the age of the patient. The success of such an approach ultimately will be determined by its impact on 5 years survival figures.

Surgical treatment:
Surgery retains its prominence as the principal means of achieving the cure of an oral squamous cell carcinoma. Surgical treatment has two distinctive phases, the resection of the tumor and the reconstruction of the defect. Reconstruction may be immediate or delayed.

Although most surgery has a curative aim, an operation can also be offered to patients with advanced, or disseminated disease where cure is unlikely. Such palliative operations have the potential to remove the pain and discomfort of the destructive tumor mass. Uncontrolled oral malignancy often becomes necrotic and may fungal on to the skin so that the patient's state is distressing to himself and his family. The improved ability to eat, speak, and breathe can make the last months of such patients much more tolerable.

Direct mortality from surgery for oral cancer has continued to decrease and is now low. Sophisticated anaesthetic techniques and intensive care have contributed to this trend as well as improved surgical methods and antibiotics. Death following primary tumor resection is rare, particularly when the airway is secured. The mortality of neck dissection is less than 1 percent and neck dissection combined with oral cancer resection results in the death of only 2-3 percent of patients (Mendelson et al, 976). Some of these deaths are the result of systemic problems. The remainder are principally due to hemorrhage or airway complications.

Local resection: Access for the surgery of oral cancers is confined by the dimensions of the mouth. A transpolar approach has severe limitations and can only be considered where small lesions are located in the anterior portion of the mouth. Skin incisions are necessary to gain sufficient access to larger lesions. These need not be disfiguring. Attention is paid to the use of natural skin contours and the staggering of incision lines. Resection proceeds along anatomical planes wherever possible. Splitting of the lower lip and osteotomy of the mandible at an appropriate site gives good exposure of more posteriorly placed lesions. While this classical approach provides the most ideal access, its cosmetic result is less acceptable than that achieved by incisions which spare the lips. The anterior floor of mouth can be dissected via a submental incision, which follows the usually obvious skin crease in this area. Where a radical neck dissection is planned concurrently with the resection of the primary lesion, the neck surgery is completed first and the incision can provide access for a continuous en bloc removal of the oral lesion. For surgery of the maxilla cheek flap is raised by means of a Weber-Ferguson incision.

Although the method of reconstruction must be planned preoperatively, no consideration should be given to it while the lesion is being resected. The extent of the resection is determined by the margins of the carcinoma and potentially involved tissue is not spared to facilitate the reconstruction. Where the patient has been treated by preoperative chemotherapy or radiotherapy, the resection must be identical in extent to that which would apply had no therapy been given, despite any apparent shrinkage of the tumor. The design of the resection must also consider the possibility of spread along local structures. In the floor of the mouth the lingual nerve and Wharton's duct can act as avenues for advancement of chords of malignant cells. The inferior alveolar canal may be involved if the tumor invades the mandible. Tumor invasion along local structures and the adequacy of the surgical margins can be cheeked at the time of surgery by the submission of tissue for frozen section examination. Although this method is not as reliable as paraffin-embedded sections for the initial diagnosis of the lesion, it is usually quite accurate in the confirmation of the presence or absence of the tumor. The surgeon must clear the site of tumor at the first attempt. The chance of resecting residual tumor at a second operation is likely to be poor as scarring and distortion of the anatomy obscure the demarcation between normal and pathological tissue.

Clinical experience over recent years has allowed the development of a more conservative approach to mandibular resection. Hemimandibulectomy is now reserved only for cases of significant bony invasion. Even in these circumstances the condylar process can some times be spared. Resection must, however, include the lingual to allow examination of the inferior alveolar nerve. If the periosteum is involved, but the bone has not obviously been disrupted, a partial thickness segment of the mandible will need to be sacrificed. If the area in question is above the mylohyoid line the lower border can be left intact. Where a tumor is adjacent to the mandible but free of the periosteum, a single plate of cortical bone is included in the resection. Such recommendations can be made following the findings of studies which noted the absence of lymphatic channels running into the mandible and freedom from involvement of the periosteum even incase where a large tumor is only a few millimeters from the mandible (Marchetta et al, 1964, 1971).

Access to deeply situated lesions can be gained by transgressing the mandible. The old approach of resecting the ramous to allow primary closure between the cheek and deeper structures is not longer tenable as modern re-constructive techniques can deal with such defects. The need to proceed with a full thickness resection of the symphysis region should always be assessed critically. This area poses particular problems in its reconstruction. The natural curvature of the bone is notoriously difficult to reproduce resulting in a considerable residual deformity.

Neck dissection: The presence of non-fixed cervical lymph node metastasizes an indication for neck dissection. Surgery seems to be still the best treatment of these metastases. Diligent examination of the neck is always necessary as cervical lymphadenopathy is not pathognomonic with metastatic carcinoma. Many of these nodes prove histologically negative. Involvement of the submandibular gland or Wharton's duct may cause swelling in the submandibular area mimicking lymph node involvement. Other nodal enlargements are reactive to secondary infection. When confirmation of the presence of malignant cells is needed, fine needle aspiration is a reliable method to employ before proceeding with the neck dissection. Neck dissection is ideally carried out in continuity with the primary resection. Bilateral metastases to the neck are difficult to treat but may be managed by simultaneous neck dissections. The airway is secured by tracheotomy. A two-stage procedure carries a lower mortality. A delay of 306 weeks between each neck dissection is usually recommended.

Appropriate management of the clinically negative neck is more controversial. Many necks are found to contain tumor following dissection, which was not apparent on clinical examination. The incidence of false negative examination of neck nodes is greater than 20 percent (Harrold 1969; Mendelson et al, 1976). Several courses of action have been advocated. Elective neck dissection is the performance of the neck dissection in the expectation of removing occult metastatic deposits. This option is particularly indicated when the primary lesion is in a site which is known to produce a high rate of neck metastases. For example, 25-45 percent of patients with carcinoma of the floor of the mouth or tongue will develop neck metastases (Jesse et al, 1970). It is also indicated when the carcinoma is anaplastic or when a patient is unlikely to be able to attend follow up appointments.

The performance of a selective neck dissection awaits the later development of clinically detectable cervical node involvement. This approach spares a number of patients the morbidity of an unnecessary neck dissection. Lesion in or adjacent to the midline may metastasize to either side. Awaiting the need for selective neck dissection is appropriate in these cases. No studies are available to show that elective neck dissection results in better survival than selective neck dissection. Vndenbrouck et al. (1980) randomized patients with T1 to T3 carcinomas of the tongue to receive either elective or selective neck dissection. The survival and disease free profiles of the two groups were not significantly different.

According to Jesse et al. (1970) only 2-5 percent of patients are likely to benefit from elective neck dissection. As this figure approaches the mortality of the procedure it would appear that its routine use is not justified.

A third alternative treatment of the clinically negative neck is irradiation. Where irradiation is used to treat the primary tumor, the field used may be extended to embrace the lymphatic tissue above the level of the thyroid cartilage or the whole of the neck as necessary. Where there is a potential for bilateral neck metastases both sides of the neck may be treated. If elective neck dissection is employed the contra-lateral side remains side remains susceptible to metastases. 4500-5000 rad delivered to the neck is effective in eradicating almost 100 percent of occult deposits in surgically undisturbed lymphatics (Fletcher 1984). If such therapy does fail, surgery is still an option. Suprahyoid neck dissection is a method of removing some of the superior nodes of the lymphatic chain usually performed in continuity with resection of lesions adjacent to the area. It is easily included in tongue, floor of mouth, and mandibular resections and carries minimal additional morbidity. The value of this procedure has been challenged by Chu and Streawitz (1978), who, after reviewing the results of three styles of neck dissection, found a high rate of metastases lower in the neck after suprahyoid neck dissection. If the suprahyoid nodes require removal, proceeding to a full neck dissection would appear to be warranted unless the neck is to be prophylactically irradiated.

The universal application of radical neck dissection was questioned by Bocca and Pignataro (1967) when they introduced the more conservative operation, the functional neck dissection. This modification spares the spinal accessory nerve, the sternocleidomastoid, and the internal jugular vein.

Reconstruction:
Surgical reconstruction: Reconstruction following resection of oral carcinoma is designed both to repair the cosmetic defect and to re-establish the functions of the lost tissues. Techniques of reconstruction have advanced rapidly over the last two decades. Despite this progress, the complexity in anatomy and function of structures such as the tongue, teeth, and jaws cannot be reproduced totally with currently available method. Fortunately, human adaptability enables most patients to tolerate the handicaps and limitations imposed on them.

Initial attempts at reconstruction should commence immediately following the removal of the carcinoma. The policy of delaying reconstruction to allow the monitoring of the tumour bed for possible recurrences has largely been abandoned. Reconstruction should also be immediate even if the resection is only designed to be palliative. This gives the patient the dignity of these final months without major deformity. The age or expectations of some patients may dictate the need for only limited attempts at reconstruction. Other patients will subject the themselves to multiple operations in an effort to improve the final result. Where specialized structures such as the teeth, nose, or eyes are expected to be lost, the maxillofacial prosthodonists can play a major role in the reconstructive process.

Both bone and soft tissue may need to be replaced following an extensive resection of the jaws. Full thickness resection of a major portion of the mandible poses a significant challenge to the reconstructive surgeon. In particular, the contour of the symphysis is particularly difficult to reproduce. With this problem in mind, conservation of the lower border of the mandible should be attempted where feasible. A variety of natural and alloplastic materials can replace mandible bone. Blocks of bone from hip or rib have commonly been used. Cancellous bone particles appear to be superior to corticocancellous blocks. This can be carried in trays of titanium, vitalium or dacron mesh, or cadaveric bone (Schwartz 1984). Metal implants have also been used but suffer from problem of rejection and instability at the site where they abut the bone.
In more recent years free bone grafts secured by micro-vascular anastamosis have been introduced. This approach is attractive in that the grafted bone remains viable and the graft may include periosteum, muscle, and skin. The ileal flap based on the deep circumflex iliac artery as described by Taylor et al. (1979) provides a large block of bone ideal for reconstructing the hemimandible. Vascularized rib grafts can also provide the contour desirable for mandible reconstruction. White these methods appear attractive, success of the graft is not assured. The techniques require great expertise and expend much operating time. As the reliability of more conventional bone graft is established these are likely to remain the mainstay of mandibular reconstruction for some time. Another alternative method of bony reconstruction in an extension of the concept of myocutaneous flap to include the osseous component. Such pedicled flap obviate the need to rely on microvascular anastomoses. These flaps have been on the pectoralis major accompanied by rib. Sternocleidomastoid with clavicular bone, and trapezius including the spine of the scapula.

Following hemimandibulectomy some patients are happy to tolerate a deformity. In these cases direct soft tissue closure is feasible. These patients often function surprisingly well, being able to masticate on the remaining hemimandible. Scar contraction, which would result in mandibular deviation, can be minimized by initial intermaxillary fixation and then inter-dental traction with training elastic bands. A guide ramp appliance can later direct the teeth into the correct occlusion.

Surgical attempts to reconstruct the maxilla following resection have not been so energetic. This is largely because prostheses have been traditionally used in this site with good success. A split-thickness skin graft is used to cover the defect and later an obturator replaces the lost tissue. The task of the prosthodontist is made less arduous if the defect is repaired primarily. The denture is then less bulky and no oronasal communication remains to interfere with its retention. A convenient source of tissue is the temporalis muscle, which is raised from the temporal fossa and rotated below the zygomatic arch. Skin coverage it not necessary as a mucosal lining spontaneously forms over the fascia surface covering the muscle (Bradley and Brockbank 1981). A portion of calvarial bone can also be included in this flap. Where denture retention requires supplementation, endosseous implants can be placed in available bone.

Soft tissue loss may be repaired by a variety of methods using tissue of local, regional, or distant origin. Primary closure is the simplest form of immediate repair. It can be used to close limited defects of the soft palate, cheek, floor of mouth, and tongue. Larger superficial defects can be lined by split skin graft or, alternatively, mucosal grafts harvested form the cheek or had palate. Mucosa is generally superior to skin. Skin functions poorly in the oral environment, it has poor wet ability when in contact with saliva, tends to shrink when placed over mobile tissue, and is often colonized by Candida albicans.

Where flaps of local tissue are available in sufficient quantity, they can provide an ideal means of reconstruction of defects n the oral cavity. These can be applied quickly as they are adjacent to the defect. They leave no defects outside of the mouth and rapid healing ensures that irradiation can be commenced quickly. The tongue is an excellent source of tissue for oral defects. The tongue has a reliable blood supply, which allows it to be safely used even if adjacent areas have been irradiated. Large defects can be filled by the 50-75 cm2 of epithelium available from the anterior hemitongue. Variations of tongue flaps are available. The flap can be based anteriorly, posteriorly, or laterally to provide tissue for the floor of the mouth, alveolar process, retromolar trigone, or palate. The remaining tongue will function well if only a partial thickness flap is raised and especially if the tip is retained. Speech therapy can speed the return to normal speech and swallowing where necessary. Buccal flaps are another convenient source of mucosa for covering the alveolar process and floor of mouth. The elasticity of this tissue ensures that mouth opening is not restricted following the mobilization of the flap.

For more extensive soft tissue deficiencies, flaps from the region of the head and neck area can provide both a bulk of tissue and a large surface area for reconstruction. These have become the favoured method of reconstruction of larger defects in the head and neck region. Two types of flaps have been used, based on different forms of blood supply. Cutaneous flaps depend on direct axial arterialization, whereas myocutaneous flaps have a non-axial, perforating musculocutaneous blood supply. At present, the success rate of undelayed myocutaneous flap are superior to those of direct coetaneous flaps. The axial blood supply is vulnerable at the extremities of the flap where of course it makes its contribution to the reconstruction. Cutaneous chest flaps include the deltopectoral flap and the anterior superior oblique chest flap. Both of these flaps derive their blood supply from the first four perforating branches of the internal mammary vessels. The deltopectoral flap was probably the most commonly used flap for head and neck reconstruction in the 1970s. Its utility suffers from the need to skin graft the donor bed. The forehead flap was originally described in 1916 and McGregor and Reid rekindled interest in it in 1966. The blood supply to the mobilized tissue is derived from the superficial temporal artery. The popularity of this flap has waned as it results in an unattractive defect, which is never fully repaired even by skilful skin grafting. One may resort to its use in elderly patients or in those unlikely to tolerate a long procedure. Its proximity to the oral cavity and the fact that it can be raised very quickly are advantageous for these patients.

The success of myocutaneous flaps is dependent on the presence of blood vessels between muscle and skin as expounded by McGraw et al. 91977). Flaps have been designed around many muscles in the neck region. The sternocleidomastoid muscle can provide a flap based superiorly or inferiorly owing to its multiple blood supply. The platysma can also provide the basis for a flap although it is poorly developed in some patients. These flaps cannot be used when metastatic disease is present in the neck. The trapezius myocutaneous flap can also be used. This tissue often provides an ideal colour match for facial tissues. The flap, which may be destined to become the most widely used, is the pectoralis major flap. This was described in 1979 by Ariyan. Its blood supply is from the pectoral branch of the thoracic artery. Primary closure of the resultant defect can be achieved in many cases. The wide range and utility of the flaps and the availability of adequate tissue which can be shaped to fill most defect make myocutaneous flaps a popular and versatile method of reconstruction.

Maxillofacial Prosthodontics :
While surgeons can provide coverage of the defect following resection of oral carcinoma, the return of functions, such as speech and mastication, and optimal cosmetic repair often rely on the skills of the prosthodontist. Early prosthodontic intervention can hasten the patient's rehabilitation and return to society. Two phases of prosthodontic care may be necessary. The initial need is for the provision of surgical splints. Arch bars are of value of secure inter-dental fixation following mandibular resection. Immobilization of the mandible allows for consolidation of the graft. If reconstruction is delayed, the fixation will minimize scar contraction. In these cases or if no reconstruction is planned, a guiding ramp is used to direct the teeth into appropriate occlusion.

Total or partial maxillectomy results in a large defect. If surgical reconstruction is restricted to the lining of the defect with skin graft, a surgical obturator is introduced intra-operatively. This has several functions. It acts as a retention device for the skin graft. It minimizes contraction of the wounds and loss of facial contour. It also allows for oral feeding to commence directly after the operation and is reassuring to the patient. The surgical obturator is designed after consultation with the surgeon regarding the extent of the resection. It is extended intra-operative with gutta percha and secured in place with circumzygomatic suspension wires where necessary. A transitional appliance may be fabricated during the period of healing or the initial one may be modified. After sufficient healing of the surgical defect, a definitive prosthetic appliance can be constructed and fitted. The maxillary defect is obturated with a hollow bulb to reduce the weight of the prosthesis. Attention must be given to its retention, cosmetic appearance, and the ability of the patient to swallow and speak. If teeth can be spared on the contralateral side to the resection, retention is enhanced.

Retention of a prosthesis, in an edentulous mandible is frequently difficult even in routine cases. In surgically mutilated mouths it becomes even more challenging. Lack of alveolar bone contour and insufficient sulcus depth generally follow attempts at reconstruction of the mandible. Where a satisfactory prosthesis cannot be worn preprosthetic surgery may be of benefit. Vestibuloplasty can recreate a denture bearing ridge in many cases. Mandibular implants such as the transmandibular implant (Bosker and van Dijk 1983) or the osseointegrated implant (Parel et al, 986) can be applied to these situations and provide the retention necessary to allow the wearing of a denture. Soft tissue loss can also be compensated for by a prosthetics. If tongue resection leaves a speech defect, the dimensions of the palatal vault can be reduced with an appliance to allow better tongue function. Where speech and swallowing are unsatisfactory the advice of the speech pathologist is of great value to the prosthodontist.

Radiotherapy:
Early this century radiation therapy was fraught with problems of toxicity. The literature of the time gave alarmist advice, suggesting that it be discarded as a treatment modality. The development of megavoltage radiation in the 1950s and subsequent refinements have allowed radiotherapy to assume a role as a major treatment modality for head and neck cancer.

The use of radiotherapy in the treatment of oral squamous carcinoma is influenced by several criteria. Most of these lesions and, equally, their cervical metastases are radiosensitive, but require high doses of radiation for significant control. Exophytic, well-oxygenated tumours tend to respond better than endophytic, hypoxic ones, larger lesions tend to be more hypoxic and hence are less curable. Bone and muscle involvement adversely affect the change of cure by radiation. Bone, being denser than soft tissues, absorbs more radiation. The likelihood of necrosis of bone following radiotherapy to lesions involving bone or adjacent to bone must be considered. Anaplastic tumours are often better treated by radiotherapy; their high mitotic rate makes them more radiosensitive.

The deposition of radiation and the death of a cell exposed to it is a random event. For a given dose increment the same proportion of cells but not the same number are killed. The dose-response curve is therefore exponential, other factors being equal. A higher dose of radiation is required to eradicate a larger population of cells. For these reasons, radiation shares the same disadvantage as surgery in being a less effective treatment modality against larger tumors.

Radiation can be delivered to the tissues by an interstitial technique or, alternatively, by external beams.

Interstitial radiotherapy: Interstitial radioactive implants have been used to treat oral cancers for many years. Initially radium and more recently iridium 192 have been employed for this purpose. The results or treating small (T1-T2) lesions with this therapy have been good. These isotopes can only be placed on a temporary basis. There is also a risk of exposure to staff and visitors while the therapy is proceeding. More recently, isotopes such as iodine 125 have gained favour. These can be introduced in many cases without the need for a general anesthetic and they need not be removed. The half- life of this isotope is approximately 60 days in comparison with 1600 years for radium 226. Typically 10 rad/hour are emitted on implantation, for a total dose of 12000 rad over 1 year. The major complication of this type of therapy ulceration, which can proceed to frank necrosis and a chronic fistula. Correct placement of implants to deliver tolerable dosage should minimize this complication. Interstitial radiation may be used on its own or in-combination with external irradiation.

External irradiation: External irradiation is conventionally delivered in the form of protons or electrons produced by megavoltage equipment. Curative doses range from 5000 to 7000 rad, typically spread over 5-7 weeks. The untoward effects on normal tissues are minimized by manipulating the direction of the beam. While the target malignant tissues receive the maximum dosage, the intervening normal tissue receives only a tolerable proportion.

Radiotherapy of large oral carcinomas is less likely to be curative owing to the large number of tumor cells, the presence of hypoxic compartments of cells, and the possibility of bone involvement. Experience with the failure to control advanced lesions by radiotherapy alone has led to the use of a combination of radiotherapy and surgery. The earlier custom of commencing treatment with radiotherapy has been reversed in many centers owing to the benefits of doing surgery first, since surgical reconstruction and healing are unimpaired if the soft tissues have not previously been irradiated. In addition, residual tumor and recurrent tumors are difficult to detect if the tissues have been severely scarred by radiotherapy.

The radiotherapist benefits by being armed with information regarding the success of the surgery. Areas in which the surgical margin is inadequate can receive specific attention. The presence of tumor in neck lymph nodes and the spread of tumor cells extranodally give further direction to the efforts of the radiotherapist. Radiation is able to destroy small tumor masses such as may be left as satellites around the periphery of a resected carcinoma. In the neck nodes, sub-clinical masses of cells may occur or small groups of residual cells may remain following neck dissection if extranodal spread has occurred. Debulking of a large tumor is less likely to contribute to a cure because the number of tumor cells is only reduced by one or two orders of magnitude. Thus, surgical debulking is only likely to be palliative.

The strategy of post-operative radiotherapy is to irradiate the surgical field and surrounding tissues with a basic dose of the order of 5000 rad. If an area has been incompletely cleared of tumor, a dose as high as 7000 rad may be used. This approach has been shown to dramatically reduce local tumor recurrence following surgery.

Radiation directed at the neck is of value if there are clinically demonstrable cervical metastases. Again it is ideally administered postoperatively, to prevent recurrence following radical neck dissection (Bartelink et al, 1983). If the neck contains no detectable masses but the behaviour of the primary lesion is expected to feature early and frequent metastatic spread, irradiating the neck is a worthwhile procedure. Sub-clinical deposits can be destroyed and the need to proceed to an elective or selective neck dissection is circumvented. The timing of postoperative radiotherapy appears to be critical. Vikram et al. (1984b) found a lower rate of recurrence in the neck when radiotherapy was commenced within 6 weeks of surgery. Those oral lesions most likely to metastasize include those of the floor of mouth and tongue, with more advanced lesions and anaplastic types particularly sharing this pre-disposition.

The use of radiotherapy for the treatment of veracious carcinoma is controversial. These exophytic lesions usually run a more benign course than squamous cell carcinoma but are locally aggressive. Anaplastic changes and metastases of these lesions following irradiation have led to a reassessment of the role of radiotherapy in the control of this disease. Curative surgery is usually possible for these cancers and thus, until doubts are resolved, it is prudent to reserve radiotherapy only for those cases where surgery is contra-indicated.

Complications of radiotherapy:
The late complications of irradiating the oral cavity are of interest to those who treat oral diseases. Exposure of the salivary glands results in destruction of the acini and fibrous replacement. Modern techniques limit the exposure of salivary tissue but the radio sensitivity of this tissue means that damage and subsequent xerostomia can still occur.

Better dental care has meant that radiation caries is not an inevitable sequela of profound xerostomia. The teeth may be temporarily protected with acrylic splints. Intensive topical fluoride therapy combined with meticulous oral hygiene limits the development and progression of caries. Exquisite cervical dentinal sensitivity can also plague these patients and may be managed by various topical desensitizing agents. Before radiotherapy commences an oral examination is mandatory so that the need for extractions or restoration of teeth can be assessed. In the motivated patient the old policy of routine dental clearance has been abandoned and is reserved for those already in dental decline. Dental infection or extractions following a course of radiotherapy to the jaws carry a risk of osteoradionecrosis. This destructive disease is difficult to treat and often follows a slowly progressive course leading to severe bone loss in the mandible. The pathology is correctly seen as ischaemic necrosis, rather than an infective necrosis, but antibiotics have a secondary role in the prevention of secondary infection. Conservative technique of management has recently been supplemented by the use of hyperbaric oxygen therapy with reportedly excellent results.

Chemotherapy:
Certain drugs have long been known to have cytotoxic activity against squamous cell carcinoma of the oral cavity. Although some dramatic effects on tumors can be seen following the administration of these drugs, complete remissions have remained rare and early recurrences have been a common feature. The role of drug therapy against squamous cell carcinomas was previously relegated to attempts to control disseminated disease where other options were not possible. Long term results were poor although valuable palliation was achieved in many cases, the patient benefiting from freedom from symptoms for several weeks or months. There are a number of reasons why the results of such therapy were poor. The potential use of the drugs was limited by toxicity considerations. The patients were often in a debilitated state from advanced malignant disease, malnourishment, and concomitant disease. The patients had often been subjected to other forms of treatment such as surgery where subsequent fibrosis and poor blood supply to the tumor limited the effectiveness of drug therapy (Despeez et al. 1970).

Today chemotherapy retains its role as a treatment modality for advanced oral malignant disease. Many attempts have been made to increase the efficacy of this form of treatment by techniques such as regional chemotherapy and by the use of large doses of drug followed by rescue from toxicity. Combinations of several drugs and techniques of combining chemotherapy with immune active agents have also been employed. Drug combination has yielded increased response rates in recent trials. Such combinations have theoretical advantages over single agents. They can be designed to attach the malignant cells during different phases of their cell cycle. They lesson the chance of survival of resistant cell lines, as mutant cells must then carry resistance to several drugs. Although increased response rates are encouraging, to date, major increases in 5-yers survival rates have not been achieved. Indications are that curative chemotherapy of advanced and disseminated oral carcinoma must await either the development of new drugs or improved adjunctive therapies.

In recent years interest has increased in the use of adjuvant chemotherapy (Mead and Jacobs 1983). This is the use of chemotherapy to complement the effects of surgery and radiotherapy. The use of chemotherapy preoperatively in curative treatment regimes is becoming more common. This strategy has a number of practical and theoretical justifications:

1. It allows the drug or drugs the maximum opportunity to exert their effects on untreated tumors.
2. Some inoperable primary tumors or neck metastases may be rendered operable by chemotherapy.
3. Sub-clinical aggregates of disease, either satellites of the primary lesions, or metastases, may be destroyed.
4. Histological analysis of the subsequently resected specimen allows assessment of the effects of the chemotherapy.
5. Other forms of treatment are not compromised by this approach.
6. Healing of the surgical site is not hindered nor are surgical complications more prevalent after chemotherapy.
7. The patients generally benefit from a rapid reduction in the pain associated with their carcinoma.
8. Some drugs also act as radiosensitizers.

The history of pre-operative chemotherapy is short. Desprez et al (1970) were amongst the first to publish results of this treatment. Recent reports indicate that response rates using combination chemotherapy can be almost 100 percent. For example, Decker et al (1983) reported a 94 percent response rate to their regime using cis-platinum and 5-fluorourcit.

If surgery does not follow chemotherapy, the assessment of the efficacy of the treatment is done on the basis of clinical impression. A complete response is then defined as the clinical disappearances of a tumor mass and a partial response as a reduction in the dimensions of a tumor. Examination of a resected specimen following chemotherapy has in some cases confirmed that a complete response has occurred, that is, a histological complete response, which is the apparent absence of viable tumor cells in the resected specimen. Those patients who respond to chemotherapy have been found to have a significantly greater chance of disease-free survival (Price et al. 1985; Rooney et al. 1985; Ervin et al, 1987).

Despite these encouraging signs in selected cases, there is not yet evidence that adjuvant chemotherapy has succeeded in positively altering the rate and pattern of disease recurrence and survival of these patients. The approach of treating advanced or aggressive carcinomas with aggressive therapy based on all three treatment modalities, namely surgery, radiotherapy, and chemotherapy, appears rational. The optimal schedule to be followed in implementing this approach has yet to be determined. Whether such complex treatment will have unexpected adverse sequela is still unclear. For example, a recent report found a disturbing rate of distant haematogenous metastases in patients receiving triple modality treatment, compared with a similar group who received radiotherapy, with or without surgery (Slotman et al, 1984). In this case, it could be postulated that the therapy is interfering with the body's capacity for immunosurveillance.

As discussed earlier, combination chemotherapy has become increasingly popular owing to the limitations of single drugs used alone. The principles governing the use of such chemotherapeutic drug combinations are:

(1) Each drug should be active at a different phase of the cell cycle;
(2) The drugs should not have overlapping toxicity;
(3) The drugs should not antagonize each other;
(4) They should be synergistic in their chemotherapeutic effect. Drugs that have been included in such combinations are hydroxyurea, cyclophosphamide, vinblastine, vincristine, and adriamycin. The plethora of permutations, which have given trials serves to illustrate that, no drug combination has yet been found to fulfill the ideal criteria and that none has produced universally good clinical results.

The oral side-effects of chemotherapy against malignant disease are of increasing interest to dental surgeons as this method of treatment becomes more widely used. Disregarding head and neck tumors, oral complications from chemotherapy of other cancer can be expected in approximately 40 percent of patients (Konzelman 1983). The most common complications are ulceration and mucositis. Others include xerostomia, opportunistic infections, gingival disease, and oral pain and hemorrhage. These problems result both from the direct action of the chemotherapeutic drugs on the mitotically active oral mucous and from the secondary effect of myelo-suppression.

Opportunistic oral infections in the temporarily immune-suppressed patient are common. They feature a range of micro-organisms that would not be pathogenic under normal circumstances. Fungal, bacterial, and viral infections are all well recognized complications. Exacerbation of periodontal disease or pulpitis can also occur in response to chemotherapy. The increasing number of patients receiving chemotherapy will result in a great need for dental care of those patients for a wide variety of previously unusual oral problems. Oral evaluation of these patients should be part of the routine preparation for chemotherapy. Prophylactic control of dental disease will prevent some future problems for these patients.

Patient after care:
Although 5-year survival figures are held to be the test of the success of treatment of malignant diseases, experience has shown that for oral carcinoma the critical period is the first years. Most recurrences occur in this initial period. Patients who are disease-free in this time will have a markedly improved prognosis. Recurrence or metastasis of oral carcinoma carries a very poor prognosis and in many cases palliation is the only possible course of management. Despite this the opportunity to treat the patient should never be lost owing to inadequate follow-up. Review appointments should be scheduled monthly for the first post-treatment year, graduating to 6-monthly check-ups after 2 years. Because of the propensity for these patients to develop second malignant lesions in adjacent sites, or in other parts of the respiratory and digestive tracts, routine examinations should continue for life.

Although the etiology of many oral carcinomas is obscure, a large proportion of those caused by known precursors are preventable. Some rare conditions such as xeroderma pigmentosum, Plummer-Vinson syndrome, and Fanconi's anemia predispose to the development of oral carcinoma. Immune-suppressed patients appear to have an increased propensity to develop neoplasm including lip and tongue cancers (Lee and Gisser 1978).Syphilis, chronic hypertrophies candidacies, and erosive lichen planus may also be precursor conditions to oral carcinoma. The role of herpes simplex virus is also being investigated. Studies of these phenomena may provide clues regarding the mechanism of oral cancer development and may later lead to therapy, which can prevent the disease in the susceptible population. For the moment we are left only with the opportunity to modify the influence that habit-forming drugs such as tobacco and alcohol have on the occurrence of this disease.

While the prevalence of oral carcinoma is destined to remain largely unaltered, further efforts should be directed towards early detection of this disease. Medical and dental schools should ensure that their graduates are skilled in oral examination and can recognize both malignant and pre-malignant lesions. The general practitioner of medicine or dentistry will be unlikely to encounter a large number of patients with a malignant oral neoplasm during his career. When this does occur, the recognition of such lesion and provision of prompt and appropriate action can be tantamount to saving the patient's life. Breast self-examination education programs can have a corollary in the oral cavity. Most oral lesions are asymptomatic. However, the tongue being so mobile and sensitive in the mouth makes it a good tool of self-examination. Unfortunately, the fear of cancer and its consequences stops many patients from reporting chronic ulcers, eruptions, or lumps until the symptoms become severe. Education programmes therefore require a twofold aim of desensitizing patients against the fear of the disease and of stressing the need to seek early consultation for any abnormality developing in the mouth.

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