A new study has reported that premenopausal women with early-stage, estrogen receptor negative (ER-) breast cancer who undergo mastectomy of both the cancerous breast and the cancer-free breast experience a five percent improvement in survival compared to those who have a mastectomy of the cancerous breast only. The authors used the U.S. Surveillance, Epidemiology, and End Results database to identify 107,106 women with breast cancer who underwent mastectomy for treatment of the cancer between 1998 and 2003. Of these women, 8,902 also underwent contralateral prophylactic mastectomy during the period.

Rates of contralateral breast cancer among young women with stages I or II disease undergoing contralateral prophylactic mastectomy were found to be independent of ER status. However, after taking into account ER status, stage and age, a reduction in breast cancer-specific mortality was found in women aged 18 to 49 years with stages I and II ER- tumors. Five year breast cancer survival for this group of women was improved with contralateral prophylactic mastectomy compared to without (88.5% versus 83.7%). The authors conclude that this survival effect is related to a higher baseline risk of contralateral breast cancer for women in this group.

When does contralateral prophylactic mastectomy make sense?

Some women with cancer in one breast will have the other breast removed to prevent subsequent breast cancer in that breast. Numerous studies have reported that most women with early stage breast cancer would not experience any improvement in survival from having a mastectomy compared to a lumpectomy plus radiation. However, all of the women in this study had a mastectomy. Therefore, the women among them with early stage breast cancer either had other tumor characteristics that prompted their oncologists to recommend a mastectomy, or they belonged to low-income or otherwise disadvantaged segments of the population who are more likely to have mastectomies for non-disease specific reasons (e.g., women who cannot make the commitment to daily radiotherapy because of work or transportation-related reasons). We suspect that the results of the study would have been even more clear had the latter group of women been excluded from it.

As the authors note, the survival benefit of contralateral prophylactic mastectomy is likely to be related to the risk of developing breast cancer in the other breast. It also likely to be related to the degree of difficulty of detecting breast cancer since the women in the study who kept their remaining breasts were likely to have had close follow-up and screening for contralateral breast cancer, especially during the first five years. Based on these considerations and the available evidence, women in the following categories who are about to have a mastectomy might consider whether contralateral prophylactic mastectomy makes sense for them:

Please note that we are not advocating contralateral prophylactic mastectomy for women in the groups outlined above, but we suggest that they discuss the possibility with their medical and surgical oncologists and make an informed decision based on their specific cases.