SUMMARY: Approximately 5% to 15% of all breast cancer patients present with local and/or regional recurrences. The role of adjuvant chemotherapy after resection of an isolated recurrence of breast cancer is unknown. To address this, in the CALOR trial, 162 patients with recurrent tumors underwent surgery and were then randomized to receive either four cycles of a multidrug chemotherapy regimen of investigator’s choice (n=85) or observation (n=77). The median age was 56 years. The treatment groups were well balanced and 68% and 58% of patients in the observation and treatment arms respectively received prior adjuvant chemotherapy. The median time to recurrence was 5 years in the treatment group and 6 years in the observation group. The primary end point was disease free survival (DFS). The 5-year DFS rate for the chemotherapy group and observation group was 69% vs 57% respectively. This translated into a relative risk reduction of 41% (hazard ratio [HR], 0.59; P = 0.045). The 5-year overall survival rate between the chemotherapy group and observation group was 88% vs 76% with a 59% reduction in the relative risk for death for patients treated with chemotherapy (HR, 0.41; P = 0.02). In patients with ER-negative tumors, the 5-year DFS was 67% in the treatment arm versus 35% in the control group (HR = 0.32; P = 0.007). This data supports the role of chemotherapy for patients with completely resected isolated locoregional recurrences of breast cancer. Aebi S, Gelber S, Láng I, et al. Presented at: CTRC-AACR San Antonio Breast Cancer Symposium, 2012. Abstract S3-2.