What is Throat cancer (Squamous Cell Carcinoma of the Tonsil)

Throat cancer or squamous cell carcinoma of the tonsil is a part of cancers of the head and neck. 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 of the cancer and cancer prognosis. Up to 30% of cancer patients with one primary head and neck tumour will have a second primary malignancy. Squamous Cell Carcinoma of the Tonsil

The pharynx is the continuation of the nose and mouth. It is a muscular tube that continues downwards through the neck and is responsible for the passage of both air (to the larynx, trachea and lungs) and food (to the oesophagus and then stomach). The pathways for food and air cross over in the pharynx. In addition, the auditory canal opens onto the upper part of the pharynx. The walls of the pharynx are composed of fascia and muscle layers all lined by a mucous membrane. The pharynx is divided into three different areas based on anatomical location: the nasopharynx (behind the nose); oropharynx (behind the mouth); and the laryngopharynx (behind the larynx).

The tonsils are a ring of lymphoid tissue around the upper part of the pharynx. They consist of the lingual tonsil in the posterior part of the tongue, the palatine tonsils and the pharyngeal tonsils. Lymphoid tissue acts as a barrier against infection.

Statistics on Throat cancer (Squamous Cell Carcinoma of the Tonsil)

This type of throat cancer is uncommon, and occurs with increasing age. The highest incidence of throat cancer is in the 6th and 7th decades with sex incidence being strongly male predominant.

Geographically, the cancerous tumor is found worldwide, but there is significant variation in incidence. The disease occurs with highest incidence in Western European countries, such as France.

Risk Factors for Throat cancer (Squamous Cell Carcinoma of the Tonsil)

This type of throat cancer shows 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 throat cancers. 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 that may then undergo malignant change to become a throat cancer. Smoking and alcohol act synergistically in the development of throat 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 smoke and the development of throat cancer – the more you smoke the greater the risk. Smokers are up to 25 times more likely to develop a cancer of the throat than their non-smoking counterparts. Passive smoking, tobacco chewing and cigar smoking are also risk factors for the development of throat cancers. Up to the point of development of overt carcinoma, many of the changes associated with cigarette smoking will reverse if the throat cancer patient quits smoking.

Alcohol consumption as a risk factor for the development of throat cancer also shows a dose-response relationship – with heavy drinkers being at greater risk. In addition, drinkers of spirits may be at greater risk of throat cancer 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 of throat cancer 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 throat cancer; and poor oral hygiene.

Progression of Throat cancer (Squamous Cell Carcinoma of the Tonsil)

This type of cancerous tumor spreads by local extension, particularly into the soft palate and through the destruction of adjacent tissue. Lymphatic invasion with spread to the cervical lymph nodes is common at theime of throat cancer diagnosis. Haematogenous spread to distant sites such as the liver, bones and lungs may have occurred at the time of diagnosis of this type of throat cancer.

How is Throat cancer (Squamous Cell Carcinoma of the Tonsil) Diagnosed?

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

Prognosis of Throat cancer (Squamous Cell Carcinoma of the Tonsil)

Early cancer of the throat detected incidentally is associated with a good prognosis. Involvement of lymph nodes in the region is associated with a poorer throat cancer prognosis. 5 year survival in early cases is more than 90%. In advanced throat cancer this drops to less than 20%. Furthermore, aetiological factors associated with cancer of the throat (primarily smoking and alcohol) render survival worse for patients even with cured or controlled tonsillar cancer. The “field cancerisation” concept means that they are at increased risk of developing second primary cancerous tumors in the head and neck region, as well as being at significant risk from cardiovascular and liver disease associated with their lifestyle.

How is Throat cancer (Squamous Cell Carcinoma of the Tonsil) Treated?

The best treatment of throat cancer is radiotherapy, but throat cancer surgery is also an appropriate option in specific cases, or the two treatments may be combined. Radiotherapy is usually preferred because it has a high cure rate, also treats regional lymph nodes and is associated with the potential for less post-treatment morbidity. Both radiotherapy and surgery are associated with similar cure rates.

Patients treated with local or regionally advance throat cancer are treated most succesfuly with a comined 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 throat cancer treatment.

Patients with recurrent and/or metastic throat cancer 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 throat cancer 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 cancerous tumors. Ideally this would include a pan- /triple-endoscopy. There are no specific screening recommendations at the moment but several clinical trials in throat cancer are currently being undertaken into the benefit of different screening techniques.

The symptoms of throat cancer 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.

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