Differences in breast cancer risk in South Asian women
Cancer Research UK scientists have discovered that the risk of breast cancer among South Asian Women in the UK differs according to their specific ethnic subgroup.
The researchers suggest that the trend may be caused by differences in lifestyle factors such as diet and body size between the two groups of women.
The researchers, based at the London School of Hygiene and Tropical Medicine, interviewed over 700 first-generation South Asian women from the West Midlands and the London area, including 240 women who had been treated for breast cancer.
The women were categorised as Gujarati Hindu, Punjabi Hindu, Punjabi Sikh, Pakistani and Indian Muslim, or Bangladeshi Muslim. The researchers began by working out which groups of women were more likely to develop breast cancer.
In general, South Asian women living in England are less likely to be diagnosed with breast cancer than their native-English counterparts. However, the researchers believe that this observation hides a more complicated picture.
The new research shows that Pakistani and Indian Muslim women are nearly twice as likely to develop breast cancer than Gujarati Hindu women.
The researchers could not tell if there was any difference in breast cancer risk between Punjabi Sikh and Hindu women, and Gujarati Hindus because the number of Punjabi women was too small to reach any firm conclusion.
The researchers then examined factors that are known to have an effect on breast cancer risk to see if they could explain these differences.
The women were asked about their diet, level of exercise, family history of breast cancer and reproductive factors such as how many children they had and whether they breast fed their children.
Valerie McCormack, the study's lead author and funded by Cancer Research UK, explains: "We already know that women who have children at younger ages, who have more children and who breast feed their children are at a lower risk of breast cancer.
"We did find differences in reproductive factors between the five groups but they did not explain the different rates of breast cancer. Pakistani and Indian Muslim women, on average, had their first child at younger ages and had more children than Gujarati Hindu women, but despite this, their breast cancer risk was higher.
"But we did find some clues when we examined the women's diet and body size. Compared to Pakistani and Indian Muslim women, the Gujarati Hindu women in this study were more likely to be vegetarian and therefore have more fibre in their diet from a higher intake of fruit and vegetables.
"On average they also had smaller waistlines which is probably the result of more physical activity. Together these may explain the lower rate of breast cancer in this group."
Research suggests that incidence of breast cancer is rising faster in South Asians than in other ethnic groups in the UK and South Asian women are less likely to go for breast screening.
Professor Robert Souhami, Director of Clinical and External Affairs for Cancer Research UK who own the British Journal of Cancer, adds: "In light of this new research, and with the recent rise in breast cancer in this group, characterising all South Asian women as 'low risk' would seem to be misleading and potentially dangerous.
"Breast cancer is a common disease and we encourage all women to be aware of the risk and attend for screening when they are invited."
- British Journal of Cancer90 (1)