Words Lim Teck Choon

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Nasopharyngeal cancer (NPC) isn’t common, but it affects a strikingly high number of Chinese and Bidayuh people. In fact, NPC has been called the Cantonese cancer, since Southern China, especially the Guangdong province and Hong Kong, reports the highest incidences of NPC in the world!

Researchers traced the migration history of people in this province across the world throughout the last few centuries, and unsurprisingly, many Chinese and the Bidayuh people in Malaysia trace their roots back to Southern China. Hence, the threat of NPC is also high among them compared to other races in this country.

This month, Dato’ Paduka Dr Balwant Singh presents an overview of the nature of and the treatment of NPC.

What’s inside the nose?

Dr Balwant explains that when we breathe in, the air travels through our nostrils to the upper part of our throat, behind our nose. As it moves down to the lungs, it passes through our nasal cavity and past the chamber known as the nasopharynx. It is located behind the nose, above the soft part (soft palate) of the mouth. From the nasopharynx, air will head down the throat and to the lungs.

A structure of note is the fossa of Rosenmüller. This is a long, deep, shallow and narrow depression situated immediately behind the eustachian tube opening. At the base of the fossa is a ball-shaped lymph node called the retropharyngeal lymph node or the node of Rouvier. Almost 50 percent of all reported NPC cases originate from this lymph node.

A cancer in Nasopharynx 

Similar to other cancers, nasopharyngeal carcinoma (NPC) arises when abnormal cells begin to grow and divide without stopping.

Breakdown of normal cellular processes that control growth, division and death. Normal cells have internal processes that will stop growth and division once there is no longer any need for such growth and division, but these processes break down in cancerous cells. Also, normal cells die once they become old or damaged, but the processes that activate cell death tend not to work properly in cancerous cells.

As a result, cancer cells will just keep growing and increasing in number, and worse, they live long past their expected life span. Consequently, these cells form masses called malignant tumours.

Invades and damages tissues. Now, imagine this tumour growing in size in a limited space. Over time, it will begin to press against surrounding tissue, eventually invading into the space of its neighbours – the throat, the bones of the surrounding region and eventually the brain. If left unchecked, this will lead to extensive damage to these organs.

Spreads to other organs in the body. Furthermore, cancer cells can spread to distant organs to form malignant tumours in those organs. Dr Balwant explains that NPC can easily spread to the lungs, liver and bones due to the rich network of lymphatic and blood vessels in the nasopharynx connecting to other parts of the body.

This process is called metastasis, and when this occurs, the cancer is said to be at its most advanced stage. Good treatment outcome is difficult to achieve at this stage.

Therefore, NPC should ideally be diagnosed and treated at its early stage. The earlier treatment begins, the better are the chances for a good treatment outcome.

In order to catch NPC at its early stage, we need to first look at the people who are most at risk (and hence should be more watchful of potential signs of NPC) as well as the signs to watch out for.

Who is at risk of NPC? 

Members of high-risk populations. Dr Balwant shares that, in Malaysia, the prevalence is much higher among the Chinese and the Bidayuh populations. Compared to them, the prevalence among Indians is fairly low, while that of the Malays is somewhere in between.

People who consume a diet high in salt. This is a theory developed after researchers examined the typical South-East Asian diet which usually includes salted vegetables, fish and eggs. Dr Balwant adds that hot soups that are often part of the Chinese diet could also be another dietary factor that increases the NPC risk.

People with a family history of cancer. Because cancers such as NPC have a genetic component that can be passed on from parent to child, people whose family members had NPC should consult an ENT specialist on how to reduce the risk and how to spot the symptoms of NPC.

People who are constantly exposed to chemicals that can cause cancer (carcinogens). This includes smokers and people who are exposed to occupational solvents or wood dust (as part of their work).

The Epstein-Barr Virus Connection

The Epstein-Barr virus has been strongly linked to NPC. A common theory is that the virus introduces its DNA into the cells in the nasopharynx, and this leads to abnormal changes in the DNA of those cells. These changes may be the ones responsible for the breakdown in control of growth, division and cell death that will eventually give rise to NPC.

Dr Balwant shares that diets high in salt and/or hot soups and foods may irritate the mucosal lining of the nose, which in turn makes it easier for the Epstein-Barr virus to infect the cells in the affected areas.

This link between NPC and the Epstein-Barr virus has led to the development of a blood test to screen for one’s risk of NPC. In this test, the blood sample is analyzed for antibodies specific for the Epstein-Barr virus – these are substances released by the immune system in the presence of the virus.

Is this test available in Malaysia? Yes. However, Dr Balwant notes that currently there is no standardized guideline for these tests. Therefore, we shouldn’t just rely solely on the test result as a confirmation as to whether we are at risk of NPC; we should instead use the result as a basis for further discussion with an ENT specialist. He or she can perform a nasal endoscopy to view the fossa of Rosenmüller for any evidence of a tumour.

How do we know if we have NPC? 

Dr Balwant shares that the people with the following symptoms are normally referred to an ENT specialist for further examination, in order to rule out NPC:

• Hearing loss (usually in one ear). Dr Balwant says that this is usually the first symptom seen among people with NPC.
• A lump on one side of the neck. Some people may have lumps on both sides. These lumps are usually not painful.
• Persistent headaches.
• Nosebleeds and/or blood in the saliva.
• Facial numbness.
• Double vision (diplopia).

Should we experience any of the above, it’s a good idea to see a doctor for further medical examination.

How is NPC treated? 

Radiation therapy. Cancer cells are very sensitive to radiation, so this remains an effective treatment option for many NPC patients. In this therapy, high-energy x-ray beams are aimed at the main nasopharyngeal tumour as well as nearby lymph nodes to destroy the cancer cells.

There are possible side effects, but most are temporary and will improve over time. One significant side effect that may be permanent is dry mouth.

“Dry mouth is caused by the salivary glands being damaged due to radiation therapy,” Dr Balwant explains. People with dry mouth cannot produce normal amounts of saliva, and hence they have problems eating and swallowing. Fortunately, there are medications (such as pilocarpine), mouth rinsers and assistive devices (such as a humidifier) that may ease the discomfort caused by dry mouth.

Chemotherapy. These are medications that are prescribed to kill cancer cells. Chemotherapy is often given alongside radiation therapy to optimize the elimination of cancer cells in the patient. It may also be given before radiation therapy begins to reduce the size of the tumour.

Patients may experience side effects from chemotherapy, but most of these effects are temporary in nature. Dr Balwant assures us that there are usually ways to reduce pain or discomfort caused by these side effects.
 

Surgery (neck dissection). This typically involves the removal of lymph nodes that contain cancer cells that do not respond well to other forms of treatment. If there is evidence of residual or recurrent tumour in the nasopharynx, it can be surgically removed via a procedure called endoscopic visualization or nasopharyngectomy.

NPC treatments may affect the patient’s speech, hearing, and ability to eat and swallow. Hence, many patients will be working closely with speech therapists and audiologists in the months following treatment completion to restore their quality of life. A dental specialist can help with management of dry mouth (if it occurs) and various aspects of dental health.

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