Contralateral prophylactic mastectomy and survival: report from the National Cancer Data Base, 1998-2002

The use of contralateral prophylactic mastectomy (CPM) has been increasing despite questionable survival benefit. We examined the effect of CPM on survival using the National Cancer Data Base. We examined overall survival on 219,983 mastectomy patients diagnosed with unilateral AJCC Stage 1-III invasive breast cancer between 1998 and 2002 of which 14,994 (7 %) underwent CPM at the time of their index mastectomy. Median follow up time was 5 years. Neoadjuvant and locally advanced breast cancers were excluded. Approximately 4 % underwent CPM in 1998 compared to 9.4 % in 2002, an ~125 % increase. CPM patients were significantly younger than non-CPM patients, on managed care plans, and were treated at high volume centers. The unadjusted hazard ratio (HR) of death was 0.55 (95 % CI 0.52-0.57) for CPM compared to unilateral mastectomy. In a multivariable Cox model adjusting for age, race, stage, grade, histology, insurance, facility characteristics, use of adjuvant hormonal, chemotherapy, and radiotherapy, and year of diagnosis, the adjusted HR was 0.88 (95 % CI 0.83-0.93; p < 0.001) which translated into an absolute 5-year benefit of 2 %. There was a differential effect of CPM by stage and age: HR = 0.88 (95 % CI 0.82-0.94; p < 0.001) in women younger than 70 with stage I/II, and HR = 0.95 (95 % CI 0.88-1.04; p = 0.28) in women with stage III or older than age 69 which translated into an absolute 5-year benefit of 1.3 %. Utilization of hormonal therapy or chemotherapy had no effect on the HR. After adjusting for confounding, the overall survival benefit for CPM is minimal at best.