Sometimes things that are so obviously intuitive still have to be validated. After a number of years of controversy, an increasing utilized surgery to prevent breast cancer is now being shown to be quite effective in both risk reduction and cancer-related mortality. The study "A Population-Based Study of Contralateral Prophylactic Mastectomy and Survival Outcomes of Breast Cancer Patients" is published in the Journal of the National Cancer Institute and can be seen here.
Contralateral prophylactic mastectomy, (CPM), a preventive procedure to remove the unaffected breast in patients with disease in one breast, clearly appears to offer a survival benefit to breast cancer patients age 50 and younger, who have early-stage disease and are estrogen receptor (ER) negative. We've known for several decades that CPM reduced the risk of developing breast cancer, but it was always more elusive to show that it actually saved lives at the end of the day. The practice of CPM has expanded significantly, with >150% growth in the number of such surgeries since the late 1990's.
How effective is CPM? Those younger than age 50 with early stage cancer with ER negative disease had a survival benefit of almost 5% at five years. For a therapeutic intervention for cancer, 5% is really substantial. You can take it to the bank that following these patients out even farther that we will show increased survival benefit with longer follow-up in the population. This is due to the fact that
- the patient's likelihood of getting a second breast cancer in the non-removed breast increases with time
- patients with prior breast cancer are among the highest risk group for developing breast cancer
Women older then 50 have a little more complicated decision. In cold, hard actuarial terms you are more likely to die from something else before a new breast cancer would kill you. On the other hand, steadily increasing lifespans of adult Americans has made some of these kind of statistical bets have to be reexamined. I would guess that the reported benefit of CPM gradually increases towards 60 years in future clinical guidelines.