Background: In patients with adenocarcinoma of the pancreas, there are no regimens. Many pre-clinical studies have shown that metformin alone or when combined with paclitaxel has antitumour effects on this tumour. We have tested here the combination of paclitaxel and metformin for patients with gemcitabine-refractory pancreatic cancer.

Methods: An uncontrolled phase II trial was carried out based on a two–stage Simon’s design, with metformin and paclitaxel for patients with locally advanced or metastatic pancreatic cancer whose disease had progressed during first line treatment with a gemcitabine-based regimen. The primary endpoint was the disease control rate at eight weeks as per response evaluation criteria in solid tumours (RECIST) 1.1. Patients received paclitaxel 80 mg/m2 weekly for three weeks every 28 days and metformin 850 mg p.o. t.i.d. continuously until progression or intolerance state was reached.

Results: Twenty patients were enrolled from July 2011 to January 2014: N = 6 (31.6%) achieved the primary endpoint, with all presenting stable disease. Median overall survival (OS) was 128 days (range 17–697) and the median progression free survival (PFS) was 44 days (range 14–210). Eight patients (40%) presented treatment-related G3-4 toxicities with the most common one being diarrhoea.

Conclusions: Despite the encouraging pre-clinical evidence of the antitumour activity of metformin in adenocarcinoma of the pancreas, the primary endpoint of the disease control rate was not met. Besides, the treatment combination was poorly tolerated and could not be studied further. This study highlights the importance of performing clinical trials to reassure preclinical or observational data.