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
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.