What is Tongue Cancer (Squamous Cell Carcinoma of the Tongue)

In oncology squamous cell cancers of the head and neck are often considered together because they share many similarities – in incidence, cancer type, predisposing factors, pathological features, treatment and prognosis. Up to 30% of patients with one primary head and neck tumour will have a second primary malignancy.

The oral cavity or mouth consists of two parts: the vestibule- which is the space between the lips and cheeks and the teeth and gums; and the mouth proper- which is internal to the teeth. The oral cavity refers to the entire contents of this area – including the cheeks, gums, teeth, tongue and palate. The functions of this region include ingestion and the first phases of digestion of food (mechanical destruction by the teeth through chewing), taste, respiration and the function of speech (the movements of the oral cavity and its components shape the sounds produced by the larynx into words).

The tongue is a very mobile muscular organ that, at rest, fills most of the oral cavity. It has many roles including taste, chewing (mastication), swallowing (deglutition), speech and cleaning the oral cavity. Its major roles are to propel a bolus of food backwards and into the pharynx to initiate swallowing and forming words to enable communication. It arises from the floor of the mouth, partly in the oropharynx, and consists of muscles covered by mucous membranes.

Statistics on Tongue Cancer (Squamous Cell Carcinoma of the Tongue)

It is relatively common, with 3% of all malignancies arising within the oral cavity. Tongue cancer is more common than all forms of oral cavity cancer except those of the lip and occurs with increasing age. It is uncommon before the age of 40 and the highest incidence of the disease is in the 6th and 7th decades with sex incidence being a 3:1 male predominance.

Geographically, the tumour is found worldwide, but there is significant variation in incidence. The disease occurs with highest incidence in Indian populations.

Risk Factors for Tongue Cancer (Squamous Cell Carcinoma of the Tongue)

All cancers of the head and neck show a strong association with alcohol consumption and tobacco smoking, particularly of cigarettes – in fact, tobacco is thought to be implicated in well over 80% of cases of squamous cell carcinoma of the head and neck. Chronic exposure of the epithelial surfaces of the head and neck to these irritants are thought to result in a “field cancerisation” sequence of hyperplasia, dysplasia and carcinoma. That is, the development of premalignant lesions may then undergo malignant change to become a cancer. Smoking and alcohol act synergistically in the development of head and neck cancer – the risk when both of these factors is present is more than double the risk of exposure to one factor alone.

There is a dose-response relationship between exposure to tobacco smoking and the development of head and neck cancer – the more you smoke, the greater the risk. Smokers are up to 25 times more likely to develop head and neck cancer than their non-smoking counterparts. Passive smoking, tobacco chewing and cigar smoking are also risk factors for the development of head and neck cancer. Up to the point of development of overt carcinoma, many of the changes associated with cigarette smoking will reverse if the patient quits smoking.

Alcohol consumptionas a risk factor for the development of head and neck cancer also shows a dose-response relationship – with heavy drinkers being at greater risk. In addition, drinkers of spirits may be at a greater risk than those who drink wine.

Chronic viral infection is also associated with the development of head and neck carcinoma. The Epstein-Barr Virus is strongly associated with the development of nasopharyngeal cancer, whilst Human Papilloma Virus, Herpes Simplex Virus and Human Immunodeficieny Virus have been associated with the development of a number of different cancers of the head and neck. This is thought to be due to their interference with the function of tumour suppressor genes and oncogenes.

Other risk factors include immune deficient states (such as post solid-organ transplant); occupational exposures to agents such as asbestos and perchloroethylene; radiation; dietary factors; a genetic predisposition to the development of the disease; and poor oral hygiene.
Cancers of the oral cavity occur with highest incidence in countries where the betel nut is chewed. With cancers of the lips, sun exposure is an additional risk factor in development.

Progression of Tongue Cancer (Squamous Cell Carcinoma of the Tongue)

This type of tumour spreads by local extension and through the destruction of adjacent tissue. Lymphatic invasion with spread to the cervical lymph nodes is common at diagnosis. Haematogenous spread to distant sites such as the liver, bones and lungs may also have occurred at the time of diagnosis.

How is Tongue Cancer (Squamous Cell Carcinoma of the Tongue) Diagnosed?

General investigations may show anaemia or abnormal liver function tests if the disease is very advanced, or due to the aetiology of the disease. In the early stages of tongue cancer general investigations tend to be normal.

Prognosis of Tongue Cancer (Squamous Cell Carcinoma of the Tongue)

Early diagnosis is the key prognostic factor in tongue cancer – influencing both tumour size and the likelihood of metastatic deposits. The 5 year disease free rate is approximately 70% in early disease, falling to less than 30% in more advanced cases. Tumours at the base of the tongue are associated with the worst prognosis due to the increased likelihood of them being diagnosed at a later stage. Furthermore, aetiological factors associated with tongue cancer (primarily smoking and alcohol) render survival worse for patients than for other malignancies. The “field cancerisation” concept means that they are at increased risk of developing second primary tumours in the head and neck region, as well as being at significant risk from cardiovascular and liver disease associated with their lifestyle.

How is Tongue Cancer (Squamous Cell Carcinoma of the Tongue) Treated?

Localised disease (T1-T2) lesions are treated with curative intent by surgery or radiation. Small lesions that are well lateralised should be excised (partial glossectomy). Larger lesions where excision would compromise speech and swallowing ability should be treated with radiotherapy.

Patients treated with local or regionally advanced disease are treated most succesfuly with a combined modality therapy of surgery, radiation therapy and chemotherapy. Concomitant chemotherapy (with 5-Fluorouracil and cisplatin) and radiation therapy appears to be the most effective sequencing of treatment.

Patients with recurrent and/or metastic disease are, with few intentions treated with palliative intent. Chemotherapy can be used for transient symptomatic benefit. Drugs with single agent activity in this setting include methotrexate, 5FU, cisplatin, paclitaxel, docetaxel. Combinations of cisplatin and 5-FU, carboplatin and 5FU, and cisplatin and paclitaxel are also used.

Improvement in symptoms is an important measurement. Specific monitoring may be by thorough serial inspection of the head and neck region – looking for disease recurrence as well as second primary tumours. Ideally this would include a pan-/triple-endoscopy. There are no specific screening recommendations at the moment but several clinical trials are currently being undertaken into the benefit of different screening techniques.

The symptoms that may require attention are somatic pain from bone metastases, visceral pain from liver or lung metastases and neurogenic pain if nerve tissue is compressed. Coughing and breathlessness from lung involvement may require specific treatment. Infection can also be a serious problem in patients with tongue cancer.