Breast cancer can be either estrogen-receptor-positive or estrogen-receptor-negative. Estrogen-receptor-positive cancer is made worse by the presence of estrogen, while estrogen has no effect on estrogen-receptor-negative cancer. Around 70% of breast cancers in women are estrogen-receptor-positive.

Some recent research has shown that chemotherapy is more helpful for women with estrogen-receptor-negative (ER - negative) cancer and that hormonal therapy, such as the use of drugs like tamoxifen helps those who are estrogen-receptor-positive.

Previously it was believed that any breast cancer larger than a centimeter should be treated with chemotherapy. But this new information about ER - negative and positive cancers over the past couple of years suggest that may not always be true.

This most recent study was published in the April 12th issue of the Journal of the American Medical Association. In a simplified summary - in 3 different clinical trials done in the 1980’s and 90’s different chemotherapy drugs were used to treat cancer. At the time ER - negative and positive was not yet understood to be important so women with both types of cancer were included in all the trials. Looking back at the data researchers discovered that the women who benefitted the most from the chemotherapy were those who wereestrogen-receptor-negative.

In the future this means that women who have ER - negative or positive cancers will be given different treatments - those who are ER - positive may or may not have any chemotherapy, etc. More research will have to be done to determine the best course of treatment in both cases.

(Technorati Tags: breast cancer, estrogen, chemotherapy, estrogen-receptor)