Dr. Sarah Hawley and her coinvestigators are to be applauded for generating insightful data regarding factors and concerns that motivate a woman to undergo contralateral prophylactic mastectomy in the setting of unilateral breast cancer (JAMA Surgery 2014 May 21 [doi:10.1001/jamasurg.2013.5689]).
Hawley et al. found that fear of recurrence was one of the strongest factors leading women to choose contralateral prophylactic mastectomy (CPM). This finding clearly demonstrates that we need to do a better job of explaining and defining the significance of (i) breast cancer local recurrence; (ii) breast cancer distant recurrence; and (iii) the development of a new/second primary breast cancer. Since cross-metastasis of a primary breast cancer to the contralateral breast is an extremely rare event, and since distant metastasis from the initial primary breast cancer tends to determine survival rates, CPM by definition will influence the incidence of only the third pattern. Furthermore, since the risk of experiencing a new contralateral malignancy is less than 1% per year for the general population of breast cancer patients, only a minority of these women will actually become bilateral breast cancer patients. Fear of recurrence is therefore a totally inappropriate reason for patients to pursue CPM, and the reasonableness of CPM to reduce the risk of a contralateral new primary breast cancer is debatable.
It can be reasonably stated that prophylactic surgery by definition is never a medically indicated necessity. Furthermore, despite the fact that a personal history of breast cancer is indeed a risk factor for developing a second primary cancer in the contralateral breast, numerous studies have demonstrated equivalent survival rates for women with unilateral breast cancer, compared with those diagnosed with bilateral/metachronous breast cancer (Cancer 2001;91:1845-53; Am. J. Clin. Oncol. 1997;20:541-5). Survival tends to be driven by the stage and effectiveness of treatment for the first cancer. By virtue of its earlier presentation, it is likely that the initially diagnosed cancer has established itself as the faster-growing malignancy with a lead time advantage in establishing distant organ micrometastatic disease; furthermore, patients with a unilateral breast cancer diagnosis are generally undergoing diligent surveillance and a contralateral malignancy is more often detected at an early stage.
Messages to our patients
It is essential for those of us who manage breast cancer to clearly emphasize several messages to our newly diagnosed breast cancer patients: First, although unilateral breast cancer increases the likelihood of developing a second primary tumor, it is certainly not inevitable, and in fact, the majority of patients are not destined to develop contralateral disease. Second, reducing the risk of being diagnosed with a contralateral breast cancer does not mitigate the mortality risk associated with the first cancer. And, finally, prophylactic mastectomy is the most aggressive and effective strategy for reducing the incidence of primary breast cancer (by approximately 90%), but it does not confer complete protection, as microscopic foci of breast tissue may be left behind in the mastectomy skin flaps, along the pectoralis, or in the axilla.
The messages above are critical: Our patients must understand that the priority is to address the known cancer. In this regard, appropriately selected patients should be encouraged to strongly consider breast-conserving surgery whenever feasible, as this low-morbidity treatment is equivalent to mastectomy from the perspective of overall survival. The question of CPM is most relevant for those patients that are ineligible for breast conservation or patients unwilling to undergo lumpectomy and breast radiation.
If a mastectomy for the cancerous breast is planned, we must then address the questions that routinely arise regarding bilateral surgery. In our efforts to clarify the reality of what CPM can and cannot achieve, we must also avoid being too dogmatic and paternalistic with our patients. There are clearly specific scenarios, as delineated in Dr. Hawley’s work, where the risk of a second primary breast cancer is likely to be considered excessive by most women, and where the decision to pursue CPM may be easier. Examples of such cases would be women known to harbor BRCA mutations or women with suspected hereditary susceptibility based on a strong family history of breast and/or ovarian cancer. The risk of a new contralateral breast cancer can be in the range of 4%-5% per year in cases of hereditary disease, compared with the general population of women with sporadic breast cancer, where the risk ranges from 0.25% to 1% per year.
Conveying an understanding of risk
Patients must understand that the risk to the contralateral breast is predominantly expressed in the future – the likelihood of having a clinically occult, incidentally detected cancer identified in the contralateral mastectomy specimen is only 6%, as demonstrated most recently by King et al. (Ann. Surg. 2011;254:2-7), and with ductal carcinoma in situ accounting for the high majority of these lesions.