Thursday, February 25, 2010

Hormone-Negative Women Under 50 Benefit Most From Double Mastectomy

Women under 50 with stage 1 to 3 hormone-receptor-negative breast cancer benefit the most from having a double mastectomy, according to a study published online today in the Journal of the National Cancer Insitute. The benefit, the researchers say, is “small”—a 4.8 percent reduced relative risk. And, they note, this is an observational study, using data from the Surveillance Epidemiology and End Results (SEER) program through the National Cancer Institute.

NOTE: This is a reduced relative risk, which means it is 4.8 percent benefit beyond whatever your original risk was, based on your tumor’s characteristics. So, if your doctor says you have a ten percent risk of recurrence, you will reduce that risk by 4.8 percent, which means a total reduced risk of less than a half percent. But, if your risk is 50 percent, you also cut that by 4.8 percent, but that give s bigger benefit—2.4 percent reduced risk. So the worse your original odds, the more you benefit.

Also, this is an observational study, using existing data on 107,106 women who had a mastectomy to treat stage 1 to stage 3 breast cancer. Among that group, 8,902 women also had their healthy breast removed. Here’s what researchers say about the data they used:

As an observational study, the results are subject to a variety of confounding factors, such as selection bias. The data used in the study were limited in terms of patient and tumor factors, such as BRCA mutation status, family history, and chemotherapy, which might affect the results.

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