A Phase II Trial of Vorinostat (Suberoylanilide Hydroxamic Acid) in Metastatic Breast Cancer: A California Cancer Consortium Study

Purpose:The primary goal of this trial was to determine the response rate of sing le-agent vorinostat in patients with metastatic breast cancer. The secondary goals included assessment of time to progression, evaluation of toxicities, and overall survival. Experimental Design: From June 2005 to March 2006, 14 patients received vorinostat, 200 mg p.o., twice daily for 14 days of each 21 day cycle. Response and progression were evaluated using Response Evaluation Criteria in Solid Tumors (RECIST) criteria. Results: The median age for all patients was 60.5 years (range, 37-88). Eight patients were estrogen receptor and/or progesterone positive, four were Her-2 positive. Sites of metastatic disease included brain, liver, lungs, bones, pelvis, pleura, chest wall, and distant lymph nodes. Patients received a median of 1.5 prior (range, 0-2) chemotherapeutic regimens for metastatic disease. Fatigue, nausea, diarrhea, and lymphopenia were the most frequent clinically significant adverse effects. The median number of cycles delivered was 2 (range, 1-20). There were no complete or partial responses, and the study was terminated after the first stage; however, 4 patients were observed with stable disease with time to progression of 4, 8, 9, and 14 months. The median number of months that patients received treatment on this study was 1.7 (range, 0.5-14). Conclusions: Although not meeting the RECIST response criteria for adequate single-agent activity, the observed tolerable toxicities and the potential for clinical benefit in terms of stable disease suggest that further assessment of vorinostat as a part of combination therapy with either chemotherapeutic or targeted agents in metastatic breast might be undertaken.