The majority of women who had double mastectomy following a breast cancer diagnosis had no major genetic or family risk factors, according to a new U.S. study, which concluded that doctors must help patients make more informed decisions in order to cut down on overtreatment of the disease.

The study, published Wednesday in the online edition of JAMA Surgery, looked at data from 1,447 women who were recently diagnosed with breast cancer. The women had reported to the Detroit and Los Angeles Epidemiology and End Results registries between 2005 and 2007 and then again four years later.

Nearly 19 per cent of the women surveyed said they strongly considered undergoing a “contralateral prophylactic mastectomy (CPM),” or the removal of both breasts.

Of those who strongly considered having the procedure, 32.2 per cent went through with the surgery, while 45.8 per cent had a unilateral mastectomy, or the removal of only the affected breast. Another 22.8 per cent had surgery to remove the cancer but not the breast.

According to the study, 68.9 per cent of patients who underwent CPM “had no major genetic or family risk factors” for the disease. Of the women who had CPM, 80 per cent said they had the surgery to prevent cancer from developing in the other breast.

The study’s authors note that few women who are diagnosed with breast cancer have a clinically significant risk of developing the disease in both breasts. They also note that there is no evidence to show that removing the unaffected breast improves survival rates.

According to the Society of Surgical Oncology, CPM should be considered only for a small number of breast cancer patients who are at high risk of developing the disease in both breasts, particularly if they have a strong family history of the disease or have tested positive for gene mutations.

"The growing rate of CPM has motivated some surgeons to question whether performing an extensive operation that is not clinically indicated is justified to reduce the fear of disease recurrence,” the authors write.

“Increased attention by surgeons coupled with decision tools directed at patients to aid in the delivery of risk and benefit information and to facilitate discussion could reduce the possibility of overtreatment in breast cancer."