Neoadjuvant exemestane for 24 weeks in postmenopausal women with hormone receptor positive stage II or IIIA breast cancer (JFMC34–0601)

Abstract

591 Background: Exemestane (EXE) is a steroidal aromatase inhibitor and has shown efficacy for not only metastatic breast cancer but also for primary breast cancer situation. Recently it is reported that preoperative treatment with EXE for 24weeks (wks) is more effective than 8 or 16wks. This study aimed to evaluate 24wks treatment of EXE in the neoadjuvant setting for hormone receptor positive, stage II/IIIA, postmenopausal breast cancer. Methods: Stage II/IIIA pts were eligible with confirmed invasive breast cancer and ER/PgR status using needle biopsy. Primary endpoints were ORR and Safety. EXE 25mg/day was administered, and if pts were evaluated CR, PR, SD at 16wks, 8wks treatment was added. Additionally rates of breast conserving surgery (BCS), nodal status, biomarker changes and the relationship between response and survival are being investigated. Results: Between March 2006 and January 2008, 116 pts were enrolled (stage IIA:77%, IIB:20%, III:3%). All pts were ER +, and 80 (69%) were PgR+, and 29 (27.1%) were HER-2+, respectively. At 24 wks, 109pts were evaluable. OR rate was 53% (58/109) and SD rate was 39% (43/109) by investigator's evaluation. Two pts withdrew due to the adverse events. At diagnosis 14 pts would have required mastectomy and after treatment only 5 pts underwent mastectomy. Central pathological review exhibited that biomarker changes during the treatment correlated with tumor response. Conclusions: EXE has shown attractive response for hormone receptor positive breast cancer in neoadjuvant setting. Especially 24wks treatment seems effective with sufficient safety and tolerability. Additional investigations are conducted to explore predictive biomarkers for response and survival. [Table: see text]