Sunday June 10, 2007

A salty cancer

The possible causes of nasopharyngeal cancer.

NASOPHARYNGEAL cancer or NPC is a dreadful cancer that afflicts mainly people of Chinese descent. It is a cancer that starts at the back of the nose, an area known as the nasopharynx. If left untreated, it can spread to the nasal cavity, oral cavity, neck nodes, lungs, bones and even to the brain.

It usually presents with sudden unexplained nose bleeds, reduced hearing in one ear from mucous retention in the middle ear (middle ear effusion), swelling of one side of the neck (neck nodes swelling) and sometimes tinnitus (noise in the ear).

The most common age at presentation is between 20 and 50 years. It rarely affects young children.

Men are two times more likely to develop NPC than women.

It is very common in China, particularly Southern China (Guangdong province and Guangxi Autonomous Region). Its incidence is also high in Chinese emigrants including Americans, Australians and Malaysians of Chinese descent.

According to Prof Rampal, Malaysian Chinese constitute 86% of all cases of NPC in Malaysia, Malays 13% whereas Indians only account for 1%.

Like most other cancers, nobody really knows what brought on this cancer. There are many theories put forward in an attempt to explain its aetiology, but most remain as theories with no definitive proof.

Genetic

The fact that NPC is so common in people of Chinese descent regardless of where they live in the world places this theory high on the list. The gene that can cause NPC has been found to be high in Chinese people.

However, the type of NPC that is inherited (meaning that it can be passed from parents to children) is rare and only accounts for 1% of all NPC cases. The majority of cases are spontaneous.

Epstein Barr virus

This virus is over-implicated as the cause of NPC. Although 80% of NPC patients have elevated antibody titres to Epstein Barr virus, more than 9% of the normal population also has elevated titres.

The majority of people infected with this virus early in life do not develop NPC as they grow older. Approximately 20% of NPC patients have never been exposed to this virus.

It is now generally accepted that Epstein Barr virus may play a modulatory role in the pathogenesis of NPC. When one undergoes blood tests to detect antibodies to Epstein Barr virus, one should not be overly concerned if the levels are elevated.

The patient should consult an ENT specialist to undergo nasendoscopy (insertion of a rigid or flexible fibreoptic scope to look at the nasopharynx) to assess whether NPC is present or not. If in doubt, one can undergo biopsy of this area.

Salted fish theory

This theory was put forward when it was discovered that the incidence of NPC was extremely high in a seafaring tribe of southern China.

Their incidence is more than double the incidence of the rest of the country.

This seafaring tribe relies mainly on dried salted fish for their natural diet. A lot of studies have since been carried out to establish the link between salted fish and NPC.

It has been found that the incidence is higher in people who consume a lot of salted fish and other dried preserved foods early in life.

It is now generally accepted that it is not the salted fish per se that causes NPC but ingestion of food with high concentration of N-nitroso compounds that increases the risk of cancer as a whole.

Nitrates and nitrites found in salted and dried preserved foods can alter the DNA of normal cells to become cancerous cells. It is also interesting to find that people who ingest diets high in fruits and vegetables (particularly high in vitamin C) have less risk of developing NPC and other cancers.

Other theories

There are other theories that state that cigarette smoking or inhaling smoke from cooking can increase the risk of NPC, but this has not been proven.

Exposure to nickel, chromium and radioactive materials has been associated with cancers of the nose and paranasal sinuses, but not with NPC.

Although salted fish has been associated with NPC, it is only one of the possible contributing factors. It is most advisable not to consume too much salted fish or other dried preserved foodstuffs. Occasional consumption of these is unlikely to give rise to NPC or other cancers.

A diet high in fruits and vegetables not only helps to reduce the risk of developing NPC, but also of other cancers.

It is of utmost importance to seek expert opinion when one develops unusual symptoms of nose bleeding, lump on the neck, reduced hearing in one ear or tinnitus as early detection and treatment of this cancer can give rise to high cure rates.

The Star Health & Ageing Advisory Panel disclaims any and all liability for injury or other damages that could result from use of the information obtained from this article.