Contralateral prophylactic mastectomy. Predictors of significant histologic findings.

BACKGROUND: Women with unilateral breast carcinoma are at increased risk for developing contralateral breast carcinoma (CBC). The authors sought to identify predictors of malignant or moderate to high-risk histologic findings in contralateral prophylactic mastectomy (CPM) specimens, and to determine the efficacy of CPM.
METHODS: The authors performed a retrospective review of 239 patients with unilateral early-stage breast carcinoma who underwent CPM. The number of CBCs expected if the contralateral breast had been left intact was calculated based on CBC rates observed in the Surveillance, Epidemiology, and End Results (SEER) database and on life-table analysis by family history.
RESULTS: In the current study, 11 patients (4.6%) had occult contralateral malignancies (4 invasive carcinomas and 7 ductal carcinomas in situ) and 44 (18.4%) patients had moderate to high-risk pathology (8 lobular carcinoma in situ, 11 atypical lobular hyperplasia, 25 atypical ductal hyperplasia). At 1846 patient-years of follow-up, only 1 patient (0.4%) developed a new CBC compared with 11 expected cancers based on SEER data. One CBC was observed among 140 patients with a family history of breast carcinoma, compared with 16 expected cancers based on life-table analysis adjusted for adjuvant therapy. The determinants of significant findings at CPM were invasive lobular histology, estrogen and progesterone receptor positivity, additional ipsilateral moderate to high-risk pathology, and age > 40 years at cancer diagnosis.
CONCLUSIONS: CPM was associated with a low risk of subsequent development of breast carcinoma. Evaluation of histologic findings in the ipsilateral breast may help to predict the likelihood of significant disease in the contralateral breast and assist in risk stratification.