A phase II clinical trial of metformin as a cancer stem cell targeting agent in stage IIc/III/IV ovarian, fallopian tube, and primary peritoneal cancer.

Abstract

5556 Background: Epidemiologic and preclinical studies suggest that Metformin has antitumor effects which may be due to an impact on cancer stem-like cells (CSC). We present a phase II trial of metformin administered in combination with chemotherapy for patients with advanced stage epithelial ovarian cancer (EOC). Primary endpoints were 18 month progression free survival (PFS) and CSC number in Metformin treated tumors. Methods: Thirty-eight patients with confirmed stage IIC(n=1)/III(n=25)/IV(n=12) EOC were treated with either neoadjuvant metformin followed primary debulking surgery and adjuvant Metformin+chemotherapy, or neo-adjuvant metformin+chemotherapy, followed by interval debulking and adjuvant chemotherapy+Metformin. Patients were evaluated for side effects, PFS and overall survival (OS). Metformin treated tumors were evaluated for the presence of CSC via FACS and sphere assays. Results: Thirty-two patients (84%) completed at least six cycles of metformin+chemotherapy. Metformin was well tolerated with only one grade III/IV treatment-related adverse event (3%) noted. Common adverse effects were diarrhea (18%) and nausea (16%). Eighteen month PFS was 65.4% (95% confidence interval 47.9-78.3), Median PFS was 21.7 months (CI-17-26.7). Estimated three year OS was 73.5% (CI-54.7-84.3) with median OS not reached after a media follow-up of 33 months. Finally, tumors treated with metformin were noted to have a 3-fold decrease in ALDH+ CSC at baseline, increased sensitivity to Cisplatin in vitro, and a reduced ability to amplify ALDH+ CSC with passage in vitro. Conclusions: This is the first prospective study of Metformin in EOC patients. Translational studies confirm an impact of metformin on CSC. Metformin was well tolerated and outcome results were favorable, supporting the use of Metformin in phase-III studies. Clinical trial information: NCT01579812.