Management of the primary tumour

Choice of treatment

The principal treatments available for primary tumours remain surgery and radiotherapy. The basic decision to be made is between radical radiotherapy and elective surgery. If the former is chosen, surgery is reserved for ‘salvage’, i.e. for biopsy proven recurrent or residual disease. If surgery is chosen, radiotherapy may be used in an adjuvant manner, either preoperatively or postoperatively, but the operation remains fundamentally the definitive curative procedure. Preferences for one or other policy vary considerably between treatment centres.

Many factors must be considered in deciding the optimum management for each individual patient. These include the sire, stage and histology of the tumour, and the medical condition and lifestyle of the patient. Ideally, every patient should be seen at a joint consultation clinic by a surgeon and radiotherapist who assess objectively and agree the optimum strategy of management for the particular individual. The following factors should influence the decision on treatment policy.

Site of origin

The choice of treatment depends on the part of the mouth in which the tumour arises. The management of primary tumours at the various anatomical sites is discussed later. In general, surgery is preferred for those tumours arising on or involving the alveolar processes; for other sires surgery and radiotherapy are alternatives.

Stage of disease

A small lesion which can be excised readily without producing any deformity or disability is, in general, best managed surgically. Surgery is also usually more appropriate for a very large mass or where there is invasion of bone, provided the tumour is operable, because of the low cure rates by radiotherapy in these circumstances. The management of lesions of intermediate stage, i.e. larger Ti, most T2 and early exophytic T3 tumours, is more controversial as policies of elective surgery or radical radiotherapy produce generally similar survival rates; hence, discussion centres on the likely functional results and morbidity of either approach.

When there is involvement of cervical lymph nodes the primary and nodes are normally both treated surgically. However, there is no clear evidence that a primary tumour is less likely to be cured by radiotherapy in the presence of lymph node metastases than in their absence.

Previous irradiation

It is not advisable to retreat a tumour arising in previously irradiated tissue. Such a tumour is likely to be relatively radioresistant because of limited blood supply. Re-irradiation of normal tissue is very likely to result in necrosis.

Field change

Where multiple primary tumours are present, or if there is extensive premalignant change, surgery is the preferred treatment. Radiotherapy in these circumstances is unsatisfactory; irradiation of the entire oral cavity causes severe morbidity and may not prevent subsequent new primary tumours arising from areas of premalignant change.

Histology

The histology report on a biopsy specimen has a relatively small influence on choice of treatment. The less common adenocarcinoma and melanoma are relatively radioresistant, and therefore should be treated surgically whenever possible. The grade of malignancy of a squamous carcinoma does not normally influence its management, there being little evidence to suggest that a well-differentiated primary should be treated differently from a poorly differentiated one.

A possible exception is the verrucous carcinoma, which is the subject of much controversy. The observation has been made that where large lesions of this histological type are treated by radiotherapy recurrences appear in some cases which are of a much more anaplastic pattern than the original primary, and it has become widely accepted that radio­therapy induces ‘anaplasric transformation’.

It seems probable that some verrucous carcinomas already contain foci of more malignant cells prior to treatment, and that these cells are the ones most likely to survive after radiotherapy and give rise to recurrence. In practice, most verrucous carcinomas present at an early stage as superficial exophytic lesions and are suitable for local excision. When they cannot be excised locally the weight of evidence suggests that they can be dealt with safely in the same way as squa­mous carcinomas of other types, and either surgery or radio­therapy be chosen as the primary treatment modality according to the site and stage of the lesion and the condition of the patient.

Age

The patient’s age is often quoted as an important factor which must be taken into account when deciding on a course of management. With a young patient there is the fear that if radiotherapy is given it may induce a malignancy in years to come; in fact, this risk is very small compared with the mortality of the disease itself. Elderly patients tend to be poor surgical risks, but they also rend to do badly with radio­therapy, especially external radiotherapy, and often deteriorate and may die as a result of the debility and poor nutritional status induced by the irradiation. Chronological age per se should not necessarily be regarded as a contraindication to surgery.

Carcinoma of the lip

Carcinoma of the lip most commonly arises at the vermilion border of the lower lip away from the line of contact with the upper lip. Only 15 per cent arise from the central third and commissure regions, and 5 per cent from the upper lip.

Initially the tumours tend to spread laterally rather than infiltrating deeply; eventually, if uncontrolled, they can spread into the anterior triangle of the neck and invade the mandible. Lymph node metastases occur late. Both surgery and radiotherapy are frequently employed and are highly effective methods of treatment, each giving cure rates of about 90 per cent.

Up to one-third of the lower lip can be removed with a or W-shaped excision with primary closure (Fig. 41.13). This method is suitable for tumours up to 2 cm in diameter. The residual defect is reconstructed by approximating and suturing the borders in three layers; mucosa, muscle and skin. Particular attention should be paid to the correct alignment of the vermilion junction. This simple procedure can readily be performed under local anaesthetic on an out-patient basis. Initially the lip will appear tight, but this improves after about 3 months.

If more than one-third of the lip is removed, primary closure results in microstomia. Therefore, for more extensive lip resections it is necessary to utilise local flaps for reconstruction. For large central defects of the lower lip, particularly in patients who do not have ageing wrinkled faces, the ‘stepladder’ approach of Johanson gives excellent cosmesis as the reconstruction advances symmetrical bilateral flaps from the lower third of the face (Fig. 41.14). This results in a mini facelift’ and the scars are concealed in the labiomental groove around the chin point. For defects more laterally, in the lower lip, the upper lip and particularly involving the commissure,   Fries’ ‘universal procedure’ gives excellent functional results with acceptable cosmesis especially in the ageing face (Fig. 41.15). With this technique, lateral facial flaps are developed following full-thickness incisions in the cheeks parallel to the branches of the facial nerve. These flaps are then advanced into the lip defect with the sacrifice of Burrows’ triangles to prevent piling up of the facial tissues.

The majority of lower lip cancers is caused by ultraviolet radiation and often the entire vermilion border will show actinic changes. Whenever these changes are seen a total lip shave would be undertaken in addition to resection of the primary tumour. The resection is reconstructed either by advancing labial or buccal mucosal flaps or, if such tissue is inadequate, by the use of a pedicled anteriorly based tongue flap. After 3 weeks the pedicle is divided and the flap finally set into the lip.

Carcinoma of the tongue

Surgery is the treatment of choice for early lesions suitable for simple intraoral excision, for tumours on the tip of the tongue and for advanced disease when surgery should be combined with postoperative radiotherapy. For intermediate-stage disease surgery and radiotherapy have similar out­comes. When performing surgical excision of less than one-third of the tongue, formal reconstruction is not necessary. Indeed, the best results are obtained by not attempting to close the defect or to apply a split-skin graft. The base of the residual defect should be fulgurated and then allowed to granulate and epithelialise spontaneously. Such treatment is relatively pain free and results in an undistorted tongue. When available a carbon dioxide laser may be used for the partial glossectomy. The postoperative course is relatively pain free, oedema is minimal and healing occurs with minimal scarring.

Any tongue carcinoma exceeding 2 cm in diameter requires at the very least a hemiglossectomy. Many such tumours will infiltrate deeply between the fibres of the hyoglossus muscle. Extensive tongue lesions often involve the floor of the mouth and alveolus. Under any of these circumstances a major resection is indicated. Access is best via a lip split and mandibulotomy (Fig. 41.16). The pull-through procedure is not recommended as it is very difficult to achieve adequate excision in all three dimensions with a limited access. As the resection opens the submandibular space the resection should include a dissection of the neck on the same side as the tumour. The type of neck dissection will depend upon the node status of the patient. A rim resection of the mandible is indicated if the tumour reaches but does not invade the alveolus. Such extensive defects require recon­struction with distant flaps. If the volume of the tongue defect does not exceed two thirds of the original tongue a radial forearm free flap with microvascular anastomoses gives a good functional result. For very large volume defects, for total glossectomy or for deeply infiltrating tumours,

when the resection extends to the hyoid bone, more bulky flaps are required to fill in the dead space and prevent food pooling.

A pectoralis major muscle flap is the best method. Whenever it is possible, without compromising the resection, at least one of the hypoglossal nerves should be preserved. If this is done, most patients will eventually relearn to swallow and will establish reasonable speech.

Carcinoma of the floor of the mouth

Floor of mouth cancers spread to involve the under surface of the tongue and the lower alveolus at a relatively early stage. Therefore, surgical excision will nearly always include partial glossectomy and marginal resection of the mandible. The resultant defect must always be reconstructed with either a local or a distant flap. It is unacceptable to advance the lateral margin of the residual tongue to the buccal mucosa as this causes very severe difficulties with speech and mastica­tion. Small tumours of the floor of the mouth that do not show deep infiltration can be treated by simple excision.

It is important that a 1-cm margin of normal-appearing mucosa be excised around the tumour. The resulting defect can either be left to granulate if a carbon dioxide laser was used for the excision, or fulgurated if diathermy excision was used. Alternatively, if the defect is large it can be repaired using bilateral nasolabial flaps tunnelled into the mouth and interdigitated anteriorly. The submandibular duct should be identified proximally, well clear of the distal margin of the excision and brought our into the floor of the mouth or lingual gutter posteriorly.

For larger lesions and those involving the ventral tongue and/or the alveolus, surgical access is gained via a midline or lateral (anterior to the mental foramen) mandibulotomy and lip split. As these extensive tumours have a high incidence of nodal involvement, the resection is undertaken in continuity with an ipsilateral neck dissection (Fig. 41.17). Recent work has demonstrated the pattern of bone invasion by carcinoma of the floor of the mouth. Invasion in the edentulous mandible is almost exclusively via deficiencies in the cortical bone of the alveolar crest. In the dentate man­dible invasion is usually via the periodontal ligament and is nearly always above the insertion of the mylohyoid muscle. Once tumour has invaded the mandible it soon enters the inferior dental canal and perineural spread occurs anteriorly and posteriorly. Consequently, in many cases the continuity of the mandible can safely be maintained provided a marginal resection is carried out which includes the inferior dental canal from the lingula to the mental foramen.

When there is evidence of gross tumour invasion of the bone resection of the mandible is mandatory. In order to avoid functional and cosmetic deformity, immediate primary reconstruction is essential. The choice lies between reconstruction with vascularised bone, a free corticocancellous graft or an alloplastic system usually supplemented with cancellous bone mush.

Carcinoma of the buccal mucosa

Lesions strictly confined to the buccal mucosa should be excised widely including the underlying buccinator muscle, followed by a quilted split-skin graft. For more extensive lesions with more complicated three-dimensional shapes, i.e. lesions extending posteriorly to the retromolar area, maxillary tuberosity or tonsillar fossa, reconstruction with a free radial forearm flap is advisable; this adapts very well to such shapes and remains soft and mobile postoperatively (Fig. 41.18).

In situations where a free flap is nor appropriate, alternatives are the buccal fat pad or the forehead flap. The buccal fat pad has proved to be a useful local flap for the reconstruction of small intraoral defects up to 3 x 5 cm. This well vascularised flap can be left raw to epithelialise spontaneously, and is used to reconstruct maxillary defects, hard and soft palate defects, and cheek and retromolar defects. For large defects at these sites its use can be combined with the temporalis muscle flap.

The use of the forehead flap, an axial flap based on the superficial temporal artery, was first described by McGregor in 1963. It is a very reliable flap able to reach most areas within the mouth including the anterior floor of the mouth. However, it is now rarely used because it results in a very obvious cosmetic defect at the donor site; it is a two-stage procedure requiring division of the pedicle at 3 weeks; and it requires the creation of a tunnel, either deep or superficial, to the zygomatic arch when the flap is needed in the oral cavity.

Carcinoma of the lower alveolus

In general, surgery is the treatment modality of choice for all alveolar carcinomas, except for patients unfit for surgery. Access is achieved via a lip-split approach. Now that the pat­terns of bone invasion are better understood, the continuity of the mandible can often be preserved by performing a marginal resection. If bone invasion is so extensive that the mandible must be resected in continuity, primary reconstruc­tion should always be undertaken as the results are always better than those of delayed reconstruction.

Several techniques are available for immediate reconstruction of the mandible. Historically, free corticocancellous grafts harvested from the iliac crest or rib grafts have been used. Provided there is a good watertight cover to the graft, results can be very satisfactory, although it is difficult to reconstruct the chin prominence with this technique. Boyne and Leake have advocated the use of cancellous bone from the ilium packed into mesh trays preformed to march the resected part of the mandible. The early dacron trays did nor prove successful, but the titanium trays currently available have given excellent results (Fig. 41.19).

Microvascular tissue transfer is currently favoured for immediate mandibular reconstruction. The radial forearm flap with a section of the radius, the compound groin flap based on the deep circumflex iliac vessels and free fibula flaps have all been advocated (Fig. 41.20). A problem with the radial flap is that the harvested bone, although restoring mandibular continuity, is barely adequate for prosthetic reconstruction.

Soft-tissue cover for all of these reconstruction techniques is critical. With microvascular free flaps the associated skin is used. For cancellous bone mush in titanium trays, and for corticocancellous grafts, the pectoralis major muscle-only flap is most useful (Fig. 41.21). The pedicle is brought up through the neck and the flap introduced into the floor of the mouth. The flap is then wrapped around the bone graft and sutured back on to itself on the labial aspect. Thus, the bone graft is totally enveloped in well-vascularised soft tissue. The mucosal resection margins are then sutured to the exposed muscle at their appropriate sires and the bare muscle allowed to epithelialise spontaneously. Such flaps withstand imme­diate postoperative radiotherapy, and the subsequent inser­tion of osteointegrated implants has not proved to be a problem.

Carcinoma of the retromolar trigone

The retromolar trigone is defined as the anterior surface of the ascending ramus of the mandible. It is roughly triangular in shape with the base being superior behind the third upper molar tooth and the apex inferior behind the third lower molar.

tumours at this site may invade the ascending ramus of the mandible. They may also spread upwards in soft tissue to involve the pterygomandibular space, which can be difficult to detect clinically or radiologically.

A lip split and mandibulotomy are needed to gain access to the retromolar region. Small defects can often be reconstructed with a masseter or temporalis muscle flap. Larger defects are best reconstructed with a free radial forearm flap which can be made to conform very well to the shape of the defect at this site.

Carcinoma of the hard palate and upper alveolus

These sites are considered together as they are closely adjacent and both are rare sites of origin of primary squamous carcinoma. A squamous carcinoma presenting at either of these sites is more likely to have arisen in the maxillary antrum than in the oral cavity. An exception is on the Indian subcontinent where carcinoma of the hard palate is seen in association with reverse smoking. tumours of minor salivary glands are much more common than squamous carcinomas on the hard palate. The vast majority of squamous carci­nomas which present in the upper gum or hard palate arises from the maxillary antrum.

A tumour confined to the hard palate, upper alveolus and floor of the antrum can be resected by conventional partial maxillectomy. A more extensive tumour confined to the infrastructure of the maxilla requires total maxillectomy. If the preoperative investigations indicate extension of disease into the pterygoid space or infratemporal fossa a more extensive procedure is necessary. The chance of obtaining a cure by surgery alone is small, and postoperative radiotherapy is essen­tial. A combined anteroposterior or lateral facial approach is required. If the tumour extends superiorly to involve the dura then a combined neurosurgical procedure will be required.

Following a maxillary resection the resulting cavity should be skin grafted to ensure rapid healing and to prevent con­tracture of the overlying soft tissues.

The defect created by surgery will require either recon­struction or a prosthesis. Various techniques have been described for reconstruction; Obwegeser described a technique using split ribs. More recently, the temporalis muscle flap has been advocated. The temporalis muscle flap is a simple tech­nique and has the advantage that it carries with it its own blood supply. It must be remembered that if such a recon­struction is to be undertaken subsequently, it is essential that at the rime of the original maxillectomy the coronoid process of the mandible is not excised, because if it is resected the blood supply to the mobilised temporalis muscle will have been compromised and the flap will necrose.

Malignant melanoma

Oral melanomas are rare. The peak age incidence is between 40 and 60 years; nearly 50 per cent are on the hard palate and about 25 per cent are on the upper gingivae. About 30 per cent of melanomas are preceded by an area of hyperpigmentation, often by many years. Pigmentation varies from black to brown, while rare nonpigmented melanomas (15 per cent of oral melanomas) are red. Oral melanomas may be flat but are usually raised or nodular, and asymptomatic initially, but may later become ulcerated and painful or bleed. Because of their rapid growth, most oral melanomas are at least 1 cm across, and approximately 50 per cent of patients have metastases at presentation (Fig. 41.22).

Clinically, size and rapid growth, particularly if associated with destruction of underlying bone or presence of metastases, are obvious indicators of a poor outcome.

Microscopically, tumour thickness, measured in millimetres from the granular cell layer to the deepest identifiable melanocyte (the Breslow thickness), is the main guide to prognosis. With cutaneous melanomas the 5-year survival rate is inversely proportional to the Breslow thickness. The poor prognosis of oral melanomas is probably due to their later detection than more conspicuous skin tumours.

Other indicators of poor prognosis are malignant melanocytes in blood vessels and multiple, or atypical, mitoses. The morphology of the melanocytes or the amount of the melanin does not appear to affect the outcome.

Once the diagnosis has been confirmed, the only hope of cure is provided by the widest possible excision followed by radical radiotherapy. There is no evidence that chemotherapy is of significant value except for palliation. The over 5-year survival rate appears to be about 5 per cent.

Management of the neck

Patients staged NO. The regional lymph nodes, although clinically impalpable, sometimes contain occult foci of malignant cells. It seems reasonable to expect, therefore, that removal or treatment of regional lymph nodes, even when clinically clear, would improve cure rates. Alternatively, it can be argued that treatment of the regional nodes in all cases is unnecessary, as only a minority has metastases in the nodes.

The arguments expressed in favour of elective block dissection are:

  the incidence of histologically involved nodes in NO necks varies from 25 to 65 per cent;

  survival rates are considerably lower in patients who develop node metastases;

  the recurrence rare following block dissection is higher in advanced disease when there is extracapsular spread or multiple nodes;

  by waiting for clinically detectable disease to develop, many patients will have a worse prognosis;

some patients fail to attend regular follow-up and may not appear again until nodal metastases are extensive;

block dissection of the neck carries negligible mortality and an acceptable morbidity;

       retrospective reviews confirm that patients undergoing elective neck dissection have higher survival rates;

  failure to control nodal metastases is a frequent cause of death.

  The arguments against elective neck dissection are that:

    it is rare for treatment to fail in the neck when the primary is controlled — only 4.5 per cent in one large series;

the incidence of histologically positive nodes in elective neck dissections exceeds the incidence of subsequent clini­cal nodal metastases, suggesting that some microscopic foci are destroyed by the body’s defences;

  the primary may recur or a second primary develop and metastasise into the dissected neck, making subsequent management very difficult;

  elective neck dissection gives no guarantee against recurrence of the tumour in the neck;

  block dissection has a considerable morbidity;

  removal of regional lymph nodes may remove a barrier to the further spread of disease;

there is no prospectively controlled trial to support the argument that elective neck dissection does improve the prognosis.

 

On balance, the weight of these arguments favours prophylactic neck dissection.

As the submandibular triangle often has to be opened as part of the resection of the primary, a function sparing elective neck dissection for tumours in the floor of the mouth and lower alveolar ridge and tongue is advocated. This dissection, in which structures such as the accessory nerve, internal jugular vein and sternocleido-mastoid muscle are preserved, can be justified. Further, a survey showed that of 501 cancers of the oral cavity, 34 per cent of nodes were found to be positive after elective radical neck dissections. Over 96 per cent of these histologically positive nodes would have been removed by a supra-omohyoid dissection.

The operation should preferably be seen as a staging procedure on which is based the decision to give radical postoperative radiotherapy. All patients with two or more positive nodes or extracapsular spread should be treated with postoperative radiotherapy.

An alternative approach is elective irradiation of the clinically negative neck, and indeed there is good evidence that this is of some benefit in preventing subsequent nodal disease. Certainly, elective irradiation to 40 Gy carries less morbidity than elective neck dissection.

Patients staged N1/N2a/N2b. At present, evidence suggests that the treatment of choice is radical neck dissection, either alone or combined with postoperative radiotherapy if multiple nodal involvement or extracapsular extension is found in the resected specimen (Fig. 41.23). In those patients unfit for radical surgery, radical external beam irradiation is indicated.

Patients staged N2c. It is uncommon for patients with oral cancer to present with bilateral nodes. When they do so, there is often a large inoperable primary tumour which is best treat­ed by external radiation. It therefore seems logical to treat the neck also by irradiation. Occasionally, particularly in young patients, bilateral neck dissection can be justified. A full radical neck dissection is undertaken on the ipsilateral side and the internal jugular vein is spared if possible on the contralateral side. Most often postoperative radiotherapy will he required for multiple nodal involvement or extracapsular spread. In such situations, severe posttreatment oedema or congestion of the face and tongue may be anticipated.

Patients staged N3. N3 indicates massive involvement, usually with fixation. Large fixed nodes are often associated with advanced primary disease with a poor prognosis. Surgery is not normally advisable: removal of the common or internal carotid artery with replacement, or extensive resection of the base of the skull, although technically feasible, is seldom advisable. Treatment is most often by external radiotherapy. In a few younger patients with resectable primaries, it is worth rendering a fixed mass in the neck operable by preoperative radiotherapy.

  Nodal metastases appearing after primary treatment

Provided that follow-up at regular intervals is rigorously maintained, it should be possible to detect a lymph node metastasis while it is still relatively small and therefore operable. Fine needle aspiration cytology is particularly useful in this situation to confirm that the palpable node is a carcinoma rather than reactive. Whenever positive, or if there is any doubt, a radical neck dissection is performed, followed by external irradiation if multiple involved nodes or extracapsular spread are found.