The practice of contralateral prophylactic mastectomy (CPM) has increased in woman with unilateral breast cancer. This highly invasive approach to the management of breast cancer has been done without hard evidence that it conveys a survival benefit. Survival Outcomes After Contralateral Prophylactic Mastectomy: A Decision Analysis by Pamela R. Portschy, Karen M. Kuntz, and Todd M. Tuttle just published in the Journal of the National Cancer Institute examines survival outcomes in women with and without CPM. The study excluded women with BRCA mutations. These mutations greatly increase the risk of getting breast, ovarian, and other cancers.
Women choose to have this procedure because of the fear of getting the disease in the remaining breast, though this likelihood is much less common than most patients suppose. Obviously this treatment is only performed on patients who have already had a mastectomy. If the cancer had been treated with any modality short of mastectomy CPM would not be a consideration. The reason for this study in the words of its authors, [W]as to assess the magnitude of the survival benefit of CPM among women with unilateral breast cancer using a simulated decision-analytic Markov model. Our aim was to provide projected long-term survival information by using a simulated Markov model for physicians and their patients when discussing breast cancer risk-reduction strategies.
[A Markov model is a recursive decision tree that guides a hypothetical cohort between mutually exclusive health states depending on transition probabilities obtained from published data. Definition from Portschy, et al]
The study concluded that there was a less than 1% 20 year survival benefit in women treated with CPM compared to those who elect not to have this treatment. This finding is not surprising. The development of a second breast cancer as stated above is not common. CPM has no effect on the response to treatment of the first cancer. And should a second cancer develop it may respond very well to treatment.
This study attracted the notice of the New York Times which published a very insightful article about it written by Peggy Orenstein who developed breast cancer in 1997. Much of the impetus towards CPM stems from an emotional response to a feared disease rather than from a dispassionate analysis of the likely benefit of such therapy. In addition to the link to the article above, I have added the whole paper as a pdf as links often go dead. The take away message is that CPM is a very aggressive treatment that likely carries little or no survival benefit. It is another example of how much of our success in the management of breast cancer, and this success has been considerable, seems to come from better treatment rather than prevention or screening.