Malay breast cancer patients fare worst

They are more likely to die than Chinese and Indian patients, new study finds

By Melissa Pang, The Straits Times, 7 Sep 2012

MALAY women with breast cancer are more likely to die than Chinese and Indian women with the disease, according to new joint research by a Singapore hospital and a Malaysian one.

They tend to be diagnosed younger with larger tumours and at later stages. Malay women also had more malignant and aggressive tumours compared to Chinese and Indians with similar tumour sizes.

The links between ethnicity and breast cancer survival rates emerged in the study of 5,200 patients from the National University Hospital (NUH) and University Malaya Medical Centre (UMMC) in Kuala Lumpur.

Previous Western studies have shown ethnicity to affect breast cancer outcomes, said one of the researchers, Assistant Professor Mikael Hartman of the National University of Singapore's Saw Swee Hock School of Public Health.

African-Americans, for instance, are known to have larger tumours at diagnosis, with the tumour already affecting the lymph nodes. They are also 50 per cent more likely to die compared to Caucasians.

The aim of this South-east Asian study was to ascertain if ethnicity affects breast cancer survival in Asians too, said Prof Hartman, who is also an NUH breast surgeon.

For the answer, researchers looked at records of about 3,700 Chinese, 970 Malays, and 530 Indians diagnosed with invasive breast cancer between 1990 and 2007.

An analysis showed the median age at diagnosis - 46 years - was significantly lower for Malay patients. Chinese patients were diagnosed at age 51, and Indians at age 53. The average size of a Malay patient's tumour was 35mm, compared to 25mm for Chinese and 30mm for Indians.

In 54 per cent of Malay patients, the tumours had spread to the lymph nodes, compared with 43 per cent of Chinese and 48 per cent of Indians.

Malays were also less likely to complete treatment. Only 80 per cent did, compared to 93 per cent of Chinese and 90 per cent of Indians. Ten years after diagnosis, 40 per cent of Malays were alive compared to 60 per cent of Chinese.

Even after adjusting for factors such as the size and nature of the tumour at diagnosis, to see if ethnicity alone affected survival, Malay women continued to be associated with higher death risks.

What are still unknown are the reasons, which could include genetic differences in tumour biology and responsiveness to treatment.

As Malay women were diagnosed at later stages of the cancer and were less likely to complete their treatment, socio-economic factors could play a part. Obesity, which is more common among Malays and Indians, can also affect breast cancer prognosis.

Researchers noted several limitations of the study. One is that it did not look at the cause of death of the breast cancer patients, which may not have been from the cancer. Lifestyle factors and co-morbidities were also not taken into account.

Co-researcher and breast surgeon Lee Soo Chin said the study suggests intrinsic biology of the tumours may be at work, since Malay women were being diagnosed at a younger age. Even if so, there are ways to overcome poorer outcomes.

"If part of the reason is that they are being diagnosed too late, then we should educate them to have mammograms, which should help a certain proportion present earlier, rather than late," she said.

Associate Professor Philip Iau, head and senior consultant of NUH's breast and trauma services in the general surgery division, said public education could target different ethnic groups to encourage more to get screened.

Researchers also noted that although Malays had poorer outcomes, Chinese women are still most at risk of getting breast cancer.

In Singapore, breast cancer is the top cancer among women, with about 1,500 cases diagnosed each year and 400 deaths. Although Medisave can be used to offset the cost of mammograms, participation remains low, said researchers. Women aged 40 and above are encouraged to be screened once a year, and those aged 50 and older once every two years.

Statistics for each race

MEDIAN AGE AT DIAGNOSIS (YEARS)

Chinese - 51

Malay - 46

Indian - 53

MEDIAN TUMOUR SIZE (DIAMETER IN MM)

Chinese - 25

Malay - 35

Indian - 30

TUMOURS THAT SPREAD TO THE LYMPH NODE (PERCENTAGE)

Chinese - 42.9

Malay - 53.6

Indian - 48

PATIENTS WHO COMPLETED TREATMENT (PERCENTAGE)

Chinese - 92.7

Malay - 79.8

Indian - 90.2

PATIENTS WHO SURVIVED AFTER 5 YEARS (PERCENTAGE)

Chinese - 75.8

Malay - 58.5

Indian - 68

PATIENTS WHO SURVIVED AT STAGE 3 AND STAGE 4 (PERCENTAGE)

Chinese - 43.7

Malay - 34.4

Indian - 43.3