Contralateral Prophylactic Mastectomy in Young Women With Breast Cancer: A Population-Based Analysis of Predictive Factors and Clinical Impact

Background and Objectives: Contralateral prophylactic mastectomy (CPM) has been increasingly common among women with unilateral invasive breast cancer (iBCa) even though the data that support it are limited. Using a population-based cohort, the objectives of the present study were to describe factors predictive of CPM in young women (≤35 years) with ibca and to evaluate the impact of the procedure on mortality. Methods: All women diagnosed during 1994–2003 and treated with CPM were identified from the Ontario Cancer Registry. Logistic regression was used to identify patient and tumour factors associated with the use of CPM. Multivariate analyses were used to assess the effect of CPM on recurrence and mortality. Results: Of 614 women identified, 81 underwent CPM (13.2%). On multivariable analysis, factors associated with CPM included negative lymph node status, negative estrogen receptor status, and initial breast-conserving surgery with re-excision. At follow-up, breast cancer–specific mortality was similar for women who did and did not undergo CPM. Conclusions: Use of CPM in young women with ibca (compared with non-use) was not associated improved breast cancer–specific mortality. Factors found to be predictive of CPM were negative lymph node status, negative estrogen receptor status, and initial breast-conserving surgery followed by re-excision.