Prognostic Factors for Metachronous Contralateral Breast Cancer: Implications for Management of the Contralateral Breast.

The absolute number of breast cancer survivors who are at risk for metachronous contralateral breast cancer (mCBC) has dramatically increased. The objectives of this study were to identify factors predictive of survival for patients with mCBC and to determine clinicopathological factors predictive of advanced mCBC. Using the Surveillance, Epidemiology, and End Results data base, we identified women, ages 18-80, diagnosed with invasive breast cancer from 1992 to 2010. We excluded patients with bilateral and stage IV primary breast cancer. Patients who developed mCBC ≥12 months from initial diagnosis were identified. Kaplan-Meier methods and Cox proportional hazards modeling were used to determine survival of patients with mCBC. Multivariate logistic regression was utilized to determine factors associated with advanced mCBC. We identified 6,673 patients who developed mCBC during our study period. The median interval between initial breast cancer and mCBC was 5 years. The strongest predictor of overall survival was the nodal status of the mCBC. Other significant prognostic factors included patient age; race; size, nodal status, estrogen receptor status, grade, and type of surgery of the initial breast cancer; grade of the mCBC; and use of radiation therapy for the mCBC. Overall, 25% of mCBCs were node positive. Younger age, black race, and characteristics of the initial breast cancer (increased size, invasive lobular histology, mastectomy treatment, and node-positivity) were significantly associated with node-positive mCBC (all p < 0.0.05). The most powerful predictor of survival for patients with mCBC is the nodal status of mCBC. Patients with advanced initial breast cancers are more likely to develop node-positive mCBC. Adherence to current surveillance and adjuvant therapy guidelines may minimize the risk and mortality of mCBCs.