If you are a breast cancer patient, this could be some of the most useful information you will ever read: according to a recent study, a preventive mastectomy to remove a second breast that you believe MIGHT become infected later is not usually beneficial.

The study was performed at the University of Texas Anderson Cancer center. After analyzing more than 100,000 cases of women who had double-mastectomies, the results indicated that “except for one sub-set of breast cancer patients, they don’t need to do this.”

The study found that the specific group that a double mastectomy would benefit were “patients under 50 and younger whose cancer is estrogen receptor negative and in the early stages.” For those over 60, there was virtually no benefit and what the article described as a “murky” benefit for patients between the ages of 50 to 60.

These results come at a time when the number of double-mastectomies has increased dramatically over the past decade. In fact, between 1999 and 2003, surgeons performed more than twice the amount of double-mastectomies due to better screening procedures that help to predict where cancer might form.

This studies results indicated that the 11% of the 107,106 patients who had a double-mastectomy had only a 5% higher survival rate than those who did not opt for the double-mastectomy. When the researchers factored out the statistics for age and other variables,  they came to the conclusion that younger women with cancer that is estrogen receptor negative in the early stages would benefit the most from a double-mastectomy.

The difference between estrogen receptor negative cancers and estrogen receptor positive cancers is that estrogen receptor negative cancers are not susceptible to treatment by tamoxifen. The main reason for this is that estrogen receptor positive cancers are controlled (and spread) by estrogen and the estrogen receptor negative cancers are not. This means that the therapies for estrogen receptor negative cancers are more limited than their estrogen-controlled counterparts and additionally that patients with estrogen receptor negative cancers have a lower survival rate in general.

In most cases the doctor should be able to determine which kind of breast cancer the patient has at the time of diagnosis.

Another important suggestion by the researchers was that those who would like a double-mastectomy should consider waiting a year to decide whether or not to have the surgery.