It's been suspected in the past, but now we finally have proof: Women who are diagnosed with breast cancer fall into different groups, and these differences are not just related to the stage of disease or their personalities.

These differences are based on their ethnicity, and ethnic differences can actually determine how well a cancer responds to particular drugs.

This discovery — that cure rates can depend in part on ethnicity — is a new challenge for doctors, since the majority of clinical trials have been conducted only on Caucasian women in North American, Europe, and Australia.

The knowledge that such differences exist among racial groups has now forced researchers to include in their research databases the ethnicity of participants in clinical trials. Scientists must now know if one drug works better for one group than for another.

Breast cancer is predominantly a disease of the economically developed world, but rates are rising in Asia and economically developing countries. Different ethnic groups also have different incidences of certain types of breast cancer, regardless of where they live. (Basal-type breast cancer is more prevalent in African-American and West-African women, for example).