Oral and oropharyngeal cancer

In global terms, oral—oropharyngeal cancer is the sixth most common malignancy. In the Western world it accounts for only 2—4 per cent of all malignant tumours, although there is now good evidence to show that the incidence is increasing particularly in younger people. By contrast, in Asia oral—oropharyngeal malignancy is the commonest malignant tumour which in parts of India accounts for no less than 40 per cent of all malignancy. It is estimated that globally there are nearly 500 000 new cases annually and that by the year 2000 there will be 1.5 million people alive with oral cancer at any one time.

Oral—oropharyngeal cancer is an almost entirely preventable disease being caused by tobacco either with or without alcohol. In the West this is mostly cigarette smoking combin­ed with alcohol abuse, the risk of both in combination being greater than the summation of the risks of each individually.

In Asia and the Far East the use of Pan and reverse smoking are the major aetiological agents. Epidemiological evidence strongly suggests that again it is the presence of tobacco in the betel quid which is the major agent, although there seems also to be some relationship to the source of slaked lime and the areca nut itself.

The incidence in women appears to be increasing and there is a worrying cohort of young patients, mostly male and particularly with tongue cancer, who show a sharp increase in incidence after a gradual fall earlier in the twentieth century. This recent trend seems not to be related to tobacco and alcohol consumption and has been observed throughout Europe and North America.

Local control of disease at the primary site and the manage­ment of neck disease have improved, yet despite this cure rates and survival rates have not improved during the last 40 years remaining at approximately 55 per cent survival at 5 years.

Both recurrence of local disease and failure to control lymphatic metastases in the neck are early events and clearly have a negative effect on 5-year survival figures. There is no doubt, however, that during the past 20 years great advances have been made in the management of oral cancer, and persis­tence of local disease and lymphatic metastasis are now less common events. Why then have cure rates not improved?

Field changes in the upper aerodigestive tract result in the phenomenon of multiple primary cancers. The longer a patient survives his or her index tumour, the greater the risk of developing a second or third primary tumour either else­where in the oral cavity or in the larynx, bronchus or oesophagus.

Even if the patient does not develop a second primary tumour, he or she is then at risk of developing distant meta­static disease. It is probable that although until recently rarely recognised during life, metastasis via the bloodstream is a relatively early event in oral cancer. Currently, 20 per cent of all cancer-related deaths in patients with a tumour in the oral cavity or oropharynx are due to distant metastasis with no evidence of disease in the head or neck. Thus, oral cancer is a ‘systemic’ disease from an early stage.

Resection

Surgical advances have been primarily in techniques of access surgery and in reconstruction. The widespread adoption of lip splitting and mandibulotomy has facilitated safe three-dimensional resections of tumours in the tongue and floor of mouth incontinuity with the lymphatics in the neck. A better understanding of the patterns of invasion of the mandible by adjacent tumour has allowed the development of rim resections, avoiding the sacrifice of mandibular continuity in many cases, without risking local recurrence. In recent years there has been the development of skull base access surgery using well-established oral and facial osteotomy techniques which have rendered previously inoperable tumours operable. This is particularly true for tumour extending into the pterygoid, infratempotal and lateral pharyngeal regions.

Reconstruction

Primary reconstruction is now the rule to the great advantage of patients. Previous reconstruction techniques were often unreliable, and when bony reconstruction was involved they were often staged. It was reasonably felt that before embarking on such prolonged and insecure techniques a period of time should be allowed to elapse to demonstrate that local recurrence was unlikely before reconstruction was attempt­ed. With current techniques based largely on muscle flaps —pectoralis major, trapezius and latissimus dorsi — and free tissue transfer, based on microvascular techniques, primary reconstruction is not only reliable but produces acceptable functional and cosmetic results.

Radiotherapy

High-energy beams, computerised planning and simulation have greatly reduced the morbidity of radiotherapy by reducing the dosage to the adjacent tissues. Teeth are no longer routinely extracted prior to radiotherapy regardless of their state, and osteoradionecrosis is now an unusual complication.

Although not a new technique, brachytherapy using iridium wire implants is regaining popularity. For suitable tumour  —Ti and early T2 tumours in mobile soft tissues — this technique delivers very high-dose local irradiation continuously with very little irradiation to adjacent tissues (Fig. 41.1). Local control rates are excellent. Currently, considerable interest is being shown in hyperfractionation techniques, whereby a higher total tumour dose can be achieved by giving more but smaller fractions of radiation.

Chemotherapy

Although many single agents or combinations of drugs can result in a response rate around 60 per cent, there is no evidence that this results in an increase in survival time or cure rate. Some centres advocate the use of induction chemotherapy prior to surgery but, again, there is no evidence based upon prospective studies that this improves survival. Palliative chemotherapy using agents such as cisplatin and 5-flurouracil are sometimes helpful for painful or fungating tumours.

Clinical aspects

Oral cancer has a predeliction for certain sites within the mouth, notably the lateral margins and ventral tongue, floor of mouth, retromolar trigone, buccal mucosa and palate. The majority — more than 85 per cent — is mucosal squamous cell carcinomas. Malignant tumours arising in the minor salivary glands are next in frequency with lymphomas, malignant melanomas, sarcomas and metastatic tumours making up the remainder.