Metformin And Stage Iv Colorectal Cancer In Elderly.

e15636 Background: It is well reported that patients with diabetes have higher risk of developing new malignancies including colorectal cancer (CRC), and previous studies also reported that antidiabetic drugs may positively impact survival in cancer patients, including CRC. The objective of this study was to determine the effect of antidiabetic drug metformin on the survival of metastatic CRC patients with type 2 diabetes. Methods: Using SEER-Medicare-linked database, we performed a retrospective study in a cohort of diabetic patients 65 years and older diagnosed with stage IV CRC from January 1, 2007 to December 31, 2013. We used multivariable regression analyses to identify factors predicting the use of metformin. Cox proportional hazards models were used to analyze the association of metformin with overall survival. Results: We identified 1804 patients with preexisting diabetes and stage IV CRC, of these 35.9 % (n = 647) patients were on metformin for diabetes. Metformin utilization increased from 7.6% in 2007 to 17.3% in 2013. Overall survival was better for patients who were on Metformin (hazard ratio [HR] 0.85, 95% CI 0.76–0.94; p = 0.002). Patients who received any cancer directed therapy including surgery, chemo or radiation were associated with improved survival (p < 0.05). The other significantly predictors of better survivals include younger age, females, Hispanic, and being married (p < 0.05). Higher comorbidity (Charlson comorbidity index 2+ vs 0) were associated with worse overall survival (P < 0.003). See table for details. Conclusions: This analysis on stage IV CRC patients based on large population-based data endorses anti-cancer effects of metformin, until confirmed by prospective studies. This analysis also highlights some other important factors and their effect on survival, which can be used for prognostication. Variables Hazard Ratio 95% CI p-value Metformin use Yes vs. no 0.85 0.76 0.94 0.002 Surgery Yes vs. no 0.67 0.60 0.74 < .0001 Radiotherapy Yes vs. no 0.63 0.49 0.81 < .001 Chemotherapy Yes vs. no 0.57 0.51 0.64 < .0001 Age Group 80+ 1.59 1.37 1.85 < .0001 Gender Female 0.87 0.78 0.97 0.013 Race Hispanic 0.80 0.66 0.97 0.021 Marital Status Married 0.77 0.67 0.88 0.000 Comorbidity Score 1 1.13 0.95 1.35 0.182 2 1.33 1.10 1.60 0.003 3 + 1.31 1.10 1.57 0.003