Can metformin change the prognosis of pancreatic cancer? Retrospective study for pancreatic cancer patients with pre-existingdiabetes existingdiabetes mellitus type 2

BACKGROUNDS: The effect of metformin on survival in patients with pancreatic cancer is controversial. AIMS: To investigate the beneficial effect of metformin in pancreatic cancer patients. METHODS: We retrospectively analyzed patients with pancreatic cancer and pre-existing diabetes mellitus type 2 who were treated at Severance Hospital (Seoul, South Korea) between May 2005 and December 2013. RESULTS: Among 237 enrolled patients, 117 patients (49.4%) were exposed to metformin. The median overall survival was 13.7 months for the metformin group versus 8.9 months for the non-metformin group (P=0.001) In univariate analysis, metformin exposure, low serum carbohydrate antigen 19-9 levels (<1000 U/mL), small tumor size (≤20 mm), no tail involvement, good performance status (ECOG 0 vs. 1 or 2), and resectable cancer stage were associated with favorable survival outcomes (all P<0.05). In multivariate analysis, in addition to low serum carbohydrate antigen 19-9 levels (