Cancer killer No.4
Southern Chinese have a high
risk of getting nasal cancer

By Adelaide Lau

F or very 100,000 people in Hong Kong, 19 get nasopha- ryngeal cancer, which is also known as nasal cancer. It is the No. 4 killer among all kinds of cancers in Hong Kong.

According to Dr. John M. Nicholls, a lecturer in the Department of Pathology at the University of Hong Kong, people living in southern China have a relatively high rate of nasal cancer.

“The nasopharynx is situated between nasal cavity and mouth cavity,” said Dr. Nicholls.

Above: A nasal cancer cell under the microscope

“Nasal cancer is a disease which is very difficult to be tested clinically in its early stage because the nasopharynx cannot be easily reached.

“When tumours start growing, there are very few symptoms until they are at the later stages.”

Dr. Leung Sing-fai, a lecturer in the Department of Clinical Oncology at The Chinese University of Hong Kong, said that nosebleeds and a swelling of lymph glands are early symptoms of nasal cancer.

Said Dr. Nicholls: “There are three causes explaining why nasal cancer is so common in southern China.

“The first one is about the diet. In the ’70s, Professor John H.C. Ho proposed that one probable cause of nasal cancer is having salted fish in the diet.”

Dr. John S. Tam, an associate professor in the Department of Microbiology at The Chinese University of Hong Kong, said, “It has been medically proved that salted fish and preserved food contain carcinogenic agents.

“Fishermen who eat comparatively more salted fish have a higher risk of getting the disease.

“Tests have been done on rats. Results showed that the rats would suffer from nasal cancer if salted fish was fed to them,” said Dr. Tam.

“Also, some tumour-promoting agents are found in some Chinese herbs. Since the southern Chinese people depend much on Chinese medicine, this may probably be a reason why the disease is so common in southern China.

“Research on this matter is still needed,” added Dr. Tam.

According to Dr. Nicholls, the second factor is related to genetics. “There is an increased risk of getting nasal cancer if a family member has been a nasal cancer patient.”

Dr. Jonathan S.T. Sham, a reader in the Department of Clinical Oncology at the University of Hong Kong, said, “The overseas Chinese suffering nasal cancer usually have ancestors originated from southern China.

“Besides, the people found to have this cancer are usually at their 50s. But those with family members suffering the disease may have it at age about 20.”

Dr. Sham said that the above reasons may explain why the risk of nasal cancer is abnormally high among southern Chinese people.

According to Dr. Nicholls, the third cause of nasal cancer is the presence of Epstein-Barr virus. This virus has been found within nasal tumours.

Dr. Tam said that the virus looks like a golf ball under the microscope.

Said Dr. Tam: “The virus has a diameter of about 75 x 10 nanometres. It is gigantic among the viruses.” The illnesses caused by this virus are usually called “kissing diseases”, which implies that the virus can be transmitted through saliva.

Dr. Tam said, “Some mothers test the temperature of congee by eating it first. When mothers feed children the congee, children get Epstein-Barr virus easily.

“The reason is that the virus may be transmitted through saliva by this traditional feeding method.

“Research showed that the saliva of every 30 out of 100 people contains the Epstein-Barr virus. The infection rate is really high,” added Dr. Tam.

Dr. Sham said that Epstein-Barr virus can also be passed on to other people by using chopsticks.

He said, “Though this cannot be proved, I think this traditional practice is a very essential cause of nasal cancer.”

However, while Dr. Leung said that there is still no direct evidence proving that the Epstein-Barr virus causes nasal cancer, he is willing to concede this much: “It is certain that there is a close relationship between Epstein-Barr virus and nasal cancer. This virus is usually found in the infected nasal cells.”

Concerning the treatments, Dr. Sham said that radiotherapy is proved to be the most effective one to date.

“Radiotherapy is able to kill the cancer cells deep inside the nasopharynx,” said Dr. Sham.

“The successful rate of recovery will be about 40 percent for the patients who are suffering nasal cancer at a later stage and up to 90 percent for those who get the treatment earlier,” said he.

One nasal cancer victim who asked that his name withheld said this about the treatment: “Forty-five times I have gone through radiotherapy. The treatment is not too harsh. But I feel thirsty whenever I talk after the treatment.”

Dr. Sham explained the reason. “As the salivary glands are all exposed to radiation, patients will be thirsty after the radiotherapy. Also, the saliva gets a bit more acidic, and this will erode the teeth.

“There are other side effects. Radiation may worsen the hearing ability. Also, the jaws may not move properly.”

Although the treatment of nasal cancer is not perfect, Dr. Nicholls believes the treatment in Hong Kong is good, compared to other places in the world.

May 1996

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