Breast cancer research needs to evaluate whether a person's ethnicity influences their response to treatment and its outcome, according to researchers at Imperial College London and published in The Lancet online.
Emerging evidence suggests that particular drugs may benefit people from one ethnic group more than others, because of differences in their genetic makeup. Most key trials looking at treatments for breast cancer have been carried out in predominantly caucasian populations in Europe, North America and Australasia.
Other populations might not respond to a drug in the same way as the Caucasian populations in these trials. The researchers suggested 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.
One example is a drug called Herceptin (trastuzumab), which is commonly used to treat people with breast cancer that is HER-2 positive. Most studies of trastuzumab have not reported the ethnicity of participants. 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 it could be argued that an individual's ethnicity could be a key factor in determining which treatments are most likely to benefit them.
Another research group at the University of Miami, Fl has been looking at whether breast tissue samples from different ethnicities include groups of differentially expressed genes. Gene expression in breast tissue from African-American women differs
from that in Caucasian and Hispanic women, just as gene expression in Hispanic women differs from both African-American and Caucasian women.
In their latest study, Baumbach et al. are focusing on women with “triple-negative” breast cancer. These women are negative for the genes for estrogen receptor (ER), progesterone receptor (PR) and HER2/neu, an epidermal growth factor receptor. This combination is associated with a particularly poor prognosis.
Thee results showed surprising differences in normal tissues; some of the differences were specific to African-Americans and were not found in Hispanics or Caucasians. They tended to have a basal-like phenotype and to have an aggressive form of breast cancer before the age of 50. The research also showed that in considering BRCA1 and BRCA2, while they had a lower incidence of deleterious germline mutations but a higher number of missense mutations. They are now doing real time PCR analyses to see if the biggest differences can be validated and proteomic research will follow in the future, making this a large and very important long term study that may influence treatment paradigms in the future.
