Do We Have Enough Evidence That Metformin Is Superior to Other Antidiabetic Drugs in Pancreatic Cancer Risk Reduction?

The current literature indicates that type 2 diabetes (T2DM) significantly increases the risk of cancer, including pancreatic cancer (PC). While metformin’s primary role is the management of T2DM, its utility extends to systemic anti-cancer effects against various cancers. Nevertheless, its impact appears limited to risk reduction, as its efficacy as a primary or adjuvant treatment for established cancer remains unproven in clinical settings. This meta-analysis aimed to evaluate the association between metformin use—both as monotherapy and in combination with other antidiabetic drugs (ADs)—and the risk of PC. We synthesized data from 16 observational studies identified through PubMed, Cochrane Library, and Clinical Trials using the Population, Intervention, Comparison, Outcomes, and Study Type (PICOT) framework. The data were analyzed using Cochrane Review Manager software 5.4, with results reported as the relative risk (RR) and 95% confidence interval (95% CI) for each comparative group; statistical significance was defined as p-value < 0.05. Our findings indicate that metformin demonstrated a significant reduction in overall PC risk when compared to the pooled group of alternative ADs. Furthermore, metformin significantly lowers PC risk compared to sulfonylureas (SUs), alpha-glucosidase inhibitors (AGIs), and insulin. Conversely, metformin use was associated with a markedly elevated PC risk relative to thiazolidinediones (TZDs) and DPP-4 inhibitors (DPP4i). Considering metformin monotherapy vs. its combination with other ADs, we found that metformin lowered the risk of PC compared to its combination with SUs and AGIs but elevated the PC risk relative to its combination with TZDs and DPP4i. To conclude, these results suggest that metformin may protect patients with T2DM from PC development. However, individual PC risk and diabetes compliance should be taken into account when deciding whether to add an additional AD(s) to metformin therapy.