Chemotherapy (CT) for isolated locoregional recurrence (ILRR) of breast cancer in ER-positive (ER+) and ER-negative (ER-) cohorts: Final analysis of the CALOR trial

513 Background: ILRR is associated with a high risk of developing breast cancer distant metastases and death. The CALOR trial (NCT00074152) investigated the effectiveness of CT following local therapy for ILRR. Previously reported results at 5-yrs median follow-up (MFU) showed significant benefit of CT for ER- ILRR, but further follow-up was required in ER+ ILRR. This report presents results at 8.8 yrs MFU within ER status cohorts. Methods: CALOR is an open-label, randomized trial for patients with completely excised ILRR after unilateral breast cancer. Eligible patients were randomized to CT (selected by the investigator; multidrug for at least 3 months recommended) or No-CT, and stratified by prior CT, hormone-receptor (ER, PR) status, and location of ILRR. Patients with ER and/or PR positive ILRR received adjuvant endocrine therapy. Radiation therapy was mandated for patients with microscopically involved margins, and anti-HER2 therapy was optional. Endpoints are disease-free survival (DFS), overall survival (OS) and breast cancer-free interval (BCFI). Results: From August 2003 to January 2010, 162 patients were enrolled: 104 ER+ and 58 ER-. The results at 8.8 years MFU in ER status cohorts are summarized in the Table (40 and 27 DFS events, respectively). The reduction in the hazard of an event associated with CT for the ER- ILRR cohort was sustained, but no benefit was observed for the ER+ cohort; interactions were significant for DFS and BCFI. The reduction in the hazard of an event seen in the ER- cohort was not apparent in ER+, with significant interactions for DFS and BCFI. Results for the 3 endpoints were consistent in multi-variable analyses adjusting for location of ILRR, prior chemotherapy, and interval from primary surgery. Conclusions: The final analysis of CALOR confirms that CT benefits patients with resected ER- ILRR. Long-term CALOR trial results do not support the use of CT for ER+ ILRR. Clinical trial information: NCT00074152. [Table: see text]