British Asians have a lower risk of breast cancer and are more likely to survive longer, a study says.
Researchers were unable to pinpoint the reasons for different risk rates
Researchers found nearly a third fewer women in the south Asian community in England and Wales develop breast cancer than among all other ethnic groups.
The London School of Hygiene and Tropical Medicine team also found more south Asians survived for five years after diagnosis than other groups.
But the researchers were unable to pinpoint the reason for the findings.
Report co-author Michel Coleman said it was "difficult to explain", suggesting diet and lifestyle could play a role.
And Dr Coleman added: "We can speculate that differential access to treatment or differences in tumour biology, or both, may contribute to the differences in survival."
However, Dr Coleman said the results could play an important role in developing health services for the south Asian population, which is the largest ethnic minority group in the UK, making up 3% of the population.
"Data on cancer incidence, survival, and mortality are vital to address the public health concerns of ethnic minorities, but such data remains sparse in the UK."
The team analysed data on 116,000 women who were diagnosed with breast cancer between 1986 and 1990.
The annual rate of breast cancer diagnosis among south Asian women was 40.5 per 100,000, compared to 57.4 per 100,000 for the rest of the population.
Researchers also found 70% of south Asian women were alive five years after diagnosis, while 67% of women from other groups were.
The study, published in the Journal of Epidemiology and Community Health, also found survival rates were 9% higher for the most affluent groups, but south Asian women were still more likely to survive.
US studies on breast cancer have also found similar results.
Nicola O'Connor, information manager at Cancer Research UK, said: "Incidence rates vary considerably from country to country and between different ethnic groups.
"Understanding the reasons for these variations is an important area of research and this study presents a number of interesting findings on breast cancer incidence and survival in south Asian women living in the UK.
"We know that south Asia has some of the lowest rates of breast cancer in the world while the UK has some of the highest."
"Previous studies have shown that migrants from low risk countries are likely to acquire the risk of their host country within two generations."
She said demographic influences, such as deprivation and access to treatment, were major influences on disease and survival rates.