Diagnosis and Treatment of Oral Cancer

This article discusses the signs, symptoms, diagnosis and treatment of mouth cancer, which currently makes up 2% of the cancers in the UK. 

Contents

Oral cancer is currently a major global health issue. In developing countries oral cavity cancer is estimated to be the third most common malignancy after cancer of the cervix and stomach. In the UK from 1995 to 2004 the number of newly diagnosed oral cancers showed an age standardised increase of 23%, and in 2005 it accounted for 2% of all cancers in the UK, which equates to 8 per 100,000 of the population[1].

Demographics of Oral Cancer

Cancer of the mouth stems from the mucosal lining (squamous epithelium) of the oral cavity. Cancer of the oral cavity is a disease affecting mainly people above the age of 55 years and only around 6% of oral cancers occur in people under the age of 45 years. It is not certain if young age provides a better chance of survival as there are conflicting reports with regard to this. However, in general it seems that the relative survival of young people (under 45 years of age) with oral cancer compares favourably with the survival of older people (45 years and older) showing a higher 5 year relative survival among young people compared with the older group. Oral cancer is known to affect more males than females with an approximate ratio of 1.5:1, respectively.

Risk Factors of Oral Cancer

Oral cancer is an “environmental” disease. There is a high incidence of the disease amongst south and southeast Asian populations (i.e. Sri Lanka, India, Pakistan and Taiwan), Latin America and the Caribbean (i.e. Brazil, Uruguay and Puerto Rico), Pacific regions, Eastern Europe (i.e. Hungary, Slovakia and Slovenia) and some parts of the Western world (i.e. France). This is due to the use of substances that adversely affect the mucosal lining of the oral cavity. Smoking, alcohol consumption and betel-quid chewing are the most important risk factors associated with oral cancer. Alcohol-drinkers have a five times higher risk of oral cancer than people who never drink. Tobacco smokers are up to six times more likely to develop oral cancer while the interactive effect of alcohol and tobacco is more than multiplicative. In fact, it is estimated that more than two thirds of mouth cancers are attributable to the combined effect of alcohol and tobacco use. Interestingly, almost a quarter of the newly diagnosed cancers in men from Sri Lanka, India, Pakistan and Bangladesh are located in the head and neck region.

Symptoms of Oral Cancer (in descending order of incidence)

  1. Non-healing ulcer or sore
  2. Sore throat, abscess or boil
  3. Sore tongue or mouth
  4. Persistent lump or swelling
  5. White or red patch
  6. Tooth ache
  7. Neck swelling 
  8. Lichen planus and/or persistent, hyperplastic oral thrush
  9. More than one of the above (in most of cases) 

Diagnosing Oral Cancer

The exact extent of any tumour and the potential spread to “regional” lymph glands in the neck is of particular importance in the diagnosis and the planning of the treatment of oral cancer. Surgery is based on the principle of complete tumour removal and therefore surgeons strive to achieve sufficient “cancer-free” margins. As a tumour mass is a three-dimensional structure, incomplete removal can occur if a surgeon considers only the tumour surface area, without sufficient knowledge of the invasion depth.

Tumour size and invasion pattern/depth is typically evaluated with the use of computer tomography (CT) or magnetic resonance imaging (MRI). Other procedures, such as ultrasonography, are used with increased frequency for the assessment of the neck status in conjunction with the use of fine needle aspiration cytology (FNAC), where a needle is used to collect a small tissue sample for microscopic evaluation.

Treatment of Oral Cancer

The traditional treatment for head and neck cancer consists of surgery and radiotherapy. Surgery remains the mainstream treatment for oral cance, whilst radical radiotherapy is associated with substantial local side effects such as a dry mouth resulting from a reduced or absent saliva flow (xerostomia). In addition, there is a risk of bone and adjacent soft tissue becoming damaged by radiotherapy (osteoradionecrosis), which causes the bone to be exposed in the mouth. Patients with tumours close to the lower jaw are particularly at high risk of experiencing this problem with radiotherapy.

In cases of early disease (stage I/II) surgery may be the single form of treatment. The surgical procedure will usually consist of an intra-oral approach where there will be a wide local removal of the tumour with a clinical margin of one centimetre of healthy surrounding tissue. The addition of chemo–radiotherapy following surgery is quite rare and will depend mainly on the results of a microscopic examination of the diseased tissue. The pattern of invasion of the tumour, namely a so-called “pushing” or “infiltrative” tumour front, the small nerve fibres’ involvement, and a low immune system response are considered as significant and independent predictors of both local recurrence and overall survival, even when adjusting for margin status.

It is interesting to note that the five year survival rates for early stage localised disease are over 80% but this drops to 40% when the disease has spread to the neck, and to below 20% for distant metastatic disease.

Treatment obviously becomes more challenging with the group of patients with advanced disease (stage III/IV) –namely when the disease spreads in more than one of the sub-sites of the oral cavity and has, potentially, already spread in the regional lymph nodes. In these cases the principles that the surgery will be based on are:

  • Exposure for adequate tumour removal.
  • Avoidance of conspicuous skin incisions.
  • Access for reconstructive surgery.

Factors Affecting Surgical Choice

The factors affecting the choice of the surgical approach are:

  • Site of the primary tumour (anterior/lateral/central/posterior).
  • Size and tumour volume.
  • Proximity of the tumour to the lower (mandible) or upper (maxilla) jaw bones.
  • Proximity of the tumour to the outer skin.

With the exception of distant metastases, the presence of cervical lymph node metastases is the most serious independent prognostic factor in patients with oral cancer.

Neck surgery has evolved considerably in recent times from radical surgery to modified radical and selective neck surgery based on the principle of removal of the lymphatic system in the neck, whilst sparing essential structures such as neck muscle/vessels/nerves which have not been advertently affected by the spread of the neck disease.

Reconstructive Surgery

Any substantial surgery to the oral cavity will lead to a considerable defect which will require reconstruction. The goals of any reconstructive method following surgery in the mouth are:

  • external wound coverage,
  • creation of a stable oral cavity,
  • restoration of bone,
  • resumption of an oral diet,
  • dental restoration,
  • restoration of cosmetic appearance.

Reconstruction following the surgical removal of large oral and oropharyngeal tumours is commonly performed with free tissue transfer and to a lesser extent with regional pedicled flaps. This means transfer of tissue (“flaps”/grafts”) from a distant site of the body and transportation in the defect of the mouth or throat. The vital blood supply of the transferred tissue is warranted with the simultaneous transfer of the vascular tree of the graft, which is “connected” with miniature surgical sutures with appropriate vessels of the neck.

The flaps used for oral cavity reconstruction can be taken from various parts of the body and can include bone as well as soft tissue.

Reduction of the morbidity at the donor site and increased versatility at the recipient site are the evolving concepts in reconstructive surgery of the head and neck. The use of “perforator” flaps – namely flaps perfused by very small vessels in the periphery of the body – represents a safe and reliable procedure in reconstructive surgery following treatment for oral cancer.

The concept of “free-style” perforator-flap surgery offers greater freedom in choosing a donor-site area because flap selection is based on the quality and volume of tissue required at the recipient site. This has led to a muscle and nerve -sparing procedure minimising the donor site morbidity whilst the versatility of the flap allows easier ‘‘bending” and ‘‘insetting” of the flap in as complex an anatomical area as the oral cavity.

These advances in modern reconstructive surgery have revolutionised the functional outcomes of major oral cancer surgery over the last 10 years so that the patients can eat, drink and speak almost normally without the social exclusions that have affected oral cancer patients in the past.

References:

  1. Cancer Research. http://info.cancerresearchuk.org/cancerstats/incidence/commoncancers
  2. Surveillance epidemiology and end results (SEER) Cancer statistics review 1975-2004. National Cancer Institute. http://seer.cancer.gov/statfacts/html/oralcav 
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