Phase 2 Trial of Metformin Combined With 5-Fluorouracil in Patients With Refractory Metastatic Colorectal Cancer

Abstract

BackgroundObservational and preclinical studies have suggested that metformin has antitumor effects in solid tumors, including colorectal cancer (CRC). However, the effects of metformin in CRC have not been tested in clinical trials. Patients and MethodsThis was a single-center, single-arm phase 2 clinical trial where histologically confirmed CRC patients with measurable and progressing metastatic disease previously treated with 5-fluorouracil (5-FU), irinotecan, oxaliplatin, and an anti–epidermal growth factor receptor (if the tumor was RAS wild type) were enrolled to receive metformin 850 mg orally continuously 2 times a day plus 5-FU 425 mg/m2 and leucovorin 50 mg intravenously weekly until disease progression, unacceptable toxicity, or withdrawal of consent. The primary end point was disease control rate at 8 weeks. ResultsAmong 50 patients included, 11 (22%) met the primary end point. The median progression-free survival was 1.8 months and the median overall survival 7.9 months. Analyzing only the 11 patients who experienced disease control at 8 weeks, their median progression-free survival was 5.6 months and their median overall survival was 16.2 months. There was a trend for prolonged median survival for obese patients (12.4 vs. 5.8 months) and those longer off 5-FU. The treatment was well tolerated; the main adverse effects were diarrhea, nausea, vomiting, and myelotoxicity. ConclusionMetformin and 5-FU showed an overall modest but intriguing activity in patients with refractory CRC in this phase 2 study. Some patients experienced long-term disease control. Further trials are needed to confirm these results, particularly in obese patients with CRC.