Breast cancer research needs to investigate how a person's ethnicity influences their response to treatment and its outcome, according to a new Comment piece in today's Lancet (18 July) by researchers from Imperial College London.

Emerging evidence suggests that particular drugs may benefit people from one ethnic group more than others, because of differences in their genetic makeup. However, most key trials looking at treatments for breast cancer have been carried out in predominantly white populations in Europe, North America and Australasia.

Other populations might not respond to a drug in the same way as the white populations in these trials, argue the researchers writing today. They suggest that clinical trials should record participants' ethnicity and analyse whether there are differences in how patients from particular ethnic groups respond to a particular therapy.

The researchers highlight the example of a drug called trasztuzumab, which is commonly used to treat people with breast cancer that is HER-2 positive. Most studies of trasztuzumab have not reported the ethnicity of participants. However, a recent study showed that people with a particular genotype responded better than others to treatment with this drug.

The genotype in question is more common in some ethnic groups than in others, so the researchers argue that an individual's ethnicity could be a key factor in determining which treatments are most likely to benefit them.

Dr Carlo Palmieri, from the Division of Surgery, Oncology, Reproductive Biology and Anaesthetics at Imperial College London and one of the authors of the piece, said: "Everyone responds differently to treatment and it's often very difficult to predict how well someone will respond to a particular drug. However, evidence is now emerging that shows how your genes might influence whether or not a particular treatment can help you.

"There are small genetic differences between people from different ethnic backgrounds and it is really important that we find out whether these genetic differences mean that certain drugs perform well in people from certain ethnic groups but not in others. It's only by doing this that we can make sure each individual receives the best possible care," added Dr Palmieri.

Breast cancer is predominantly a disease of the economically developed world, but rates are rising rapidly in Asian and economically developing countries. Different ethnic groups have different incidences of certain kinds of breast cancer regardless of where they live. For example, there is a greater incidence of basal type breast cancer within African-American and West African populations. People's outcomes from breast cancer also vary between ethnic groups for reasons which are still not entirely clear.