Pharynx cancer: Squamous cell carcinoma of the pharynx

• What is Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• Statistics on Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• Risk Factors for Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• Progression of Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• Symptoms of Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• Clinical Examination of Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• How is Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx) Diagnosed?
• Prognosis of Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx)
• How is Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx) Treated?

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

Pharynx cancer or squamous cell carcinoma of the pharynx is a cancer 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 and prognosis. Up to 30% of patients with one primary head and neck tumour will have a second primary malignancy.

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).

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

This type of cancer uncommon, and occurs with increasing age. The highest incidence of pharynx 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. Pharynx cancer occurs with highest incidence in Asian countries; particularly in the Chinese.

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

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 pharynx cancer. 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 pharynx cancer. Smoking and alcohol act synergistically in the development of pharynx 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 pharynx cancer – the more you smoke the greater the risk. Smokers are up to 25 times more likely to develop pharynx cancer than their non-smoking counterparts. Passive smoking, tobacco chewing and cigar smoking are also risk factors for the development of pharynx cancer. Up to the point of development of overt carcinoma, many of the changes associated with cigarette smoking will reverse if the cancer patient quits smoking.

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

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

This type of cancerous tumor spreads by local extension and through the destruction of adjacent tissue, with bony infiltration being a common early finding. Cancerous tumors can invade the orbit (the eye), the skull (and hence the cranial fossae) and the bones of the spinal cord. Lymphatic invasion with spread to the cervical lymph nodes is common at cancer diagnosis. Haematogenous spread to distant sites such as the liver, bones, lungs and spleen may also have occured at the time of cancer diagnosis.

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

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

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

Pharynx cancer tends to grow silently with symptoms of cancer often not evident until the cancerous disease is quite advanced. Early pharynx cancer detected incidentally is associated with a relatively good cancer prognosis. Involvement of lymph nodes in the region is associated with a poorer prognosis of the cancer. In most cases, the 5 year survival rate is between 15% and 70%. However, in some cancer patients the course of pharynx cancer is more indolent with a long survival rate even if the cancerous disease itself has been controlled but not cured.

Furthermore, aetiological factors associated with pharynx cancer (primarily smoking and alcohol) render survival worse for patients even with cured or controlled pharyngeal 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 Pharynx Cancer (Squamous Cell Carcinoma of the Pharynx) Treated?

The most popular treatment of pharynx cancer radiotherapy. Surgery is not generally indicated in the treatment of pharyngeal cancer due to the inaccessibility of the site of the cancerous tumour and the high likelihood of macro and micro metastases at the time of diagnosis of the cancer. In addition, pharyngeal carcinomas and their metastatic deposits show a good response to radiotherapy, but high doses are commonly required. Radiotherapy fields should be quite extensive to minimise the likelihood of pharynx cancer recurrence. Cancer surgery can play a role in the management of very small lesions.

Chemotherapy has not been found to be of much benefit in the clinical trials conducted to date, but adjuvant cisplatin and 5-FU can be given.

Improvement in symptoms of cancer is an important measurement. Specific monitoring may be by thorough serial inspection of the head and neck region – looking for cancerous disease recurrence as well as second primary cancerous tumors. Ideally this would include 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 pharyngeal cancer (particularly pneumonia in patients with lung metastases).