Breast cancer: Gene mutation study offers hope

PUBLISHED : Tuesday, 23 October, 2012, 12:00am
UPDATED : Tuesday, 23 October, 2012, 10:08am

Chinese breast and ovarian cancer patients have been found to have the same pattern of gene mutations in a study done by a local medical researcher, raising hopes that a tailor-made genetic test can be developed to help Chinese fend off cancer.

The study by Hong Kong Hereditary Breast Cancer Family Registry analysed 535 Chinese breast and ovarian cancer patients for hereditary mutations in the genes known as BRCA, which increase the risk for both cancers.

These gene mutations have mainly been reported in Caucasians and Ashkenazi Jews (who have mainly central and eastern Europe an ancestry) and its prevalence is less known among Chinese and other Asians.

Ten per cent of the study subjects were found to carry the BRCA mutations. Of these, about one in four carry mutations in the four same spots in DNA genetic sequencing. The results of the study were published last month in PLOS ONE, an open-access peer-reviewed scientific journal published by the US-based Public Library of Science.

Dr Ava Kwong Hoi-wai, chairwoman of the registry and chief of Queen Mary Hospital's breast surgery division at University of Hong Kong, says the findings are significant in that they might prove that Chinese cancer sufferers carry a unique pattern of gene mutations.

Everyone has BRCA genes. BRCA1 and BRCA2 are known as tumour suppressors because they help repair damaged DNA in cells that have divided improperly. But when either of those genes mutate, the repair process can go awry.

According to the US National Cancer Institute, the risk of breast cancer in the general population is 12 per cent, but those who are BRCA-positive carry a 60 per cent risk. The risk for ovarian cancer goes up from 1.4 per cent to between 15 per cent and 40 per cent.

Kwong says BRCA-positive males are 60 per cent more like to suffer from breast cancer and are four times more at risk of prostate cancer than men without the mutations.

"Most Jewish breast cancer sufferers are found to carry mutations in three spots in the BRCA. When those Jewish people predisposed to develop cancer [because family members have been struck by it] come for genetic screening tests, doctors can prescribe genetic tests aimed at the three spots, sparing the high financial and time cost in mapping out the entire gene for an initial first screen," she says.

"Every ethic race carries different genetic mutations. [Non-Chinese] carry more BRCA1 mutations, while Chinese carry more BRCA2 mutations. Forty-two per cent of the mutations found in our study have never been reported in other ethnicities."

BRCA mutations have been known for a decade, but until recently there have been no studies of the Asian or Chinese population.

Kwong says more studies are needed to prove the mutation patterns found in this study are unique to Chinese. To that end, the registry is collaborating with organisations and universities in Canada, Britain and the mainland to study pockets of the Chinese population. The study is expected to take one to two years.

"If the patterns found in Chinese who live in America or Britain are like those in Hong Kong, it can lead to a complete overhaul of testing methods," says Kwong. "For future test subjects, we can do tests on the Chinese-specific four spots first before we do a comprehensive test."

The registry has tested 903 patients and 214 family members since being set up five years ago. Tests are also available at the cancer genetics clinic at the Hong Kong Sanatorium and Hospital.

Kwong says those who have family members suffering from breast or ovarian cancer should check their clinical status for the genetic tests.

"Not everyone needs to undergo genetic tests. Those who were struck by breast cancer before they reached 45 and those with more than three family members suffering from breast cancer, or with family members with breast and ovarian cancers, have greater chance of carrying mutations."

Testing the first family member, usually the cancer patient, costs HK$18,000 to HK$25,000 as the entire gene must first be mapped out. Tests on other family members cost about HK$3,000.

This month, the registry has collaborated with restaurants on Pink Desserts for a Cause. Part or all of the proceeds from the sale of special pink desserts go to the registry for patient support, research and education. For more details, go to