To the Editor: The case-control study by Dr Li and colleagues1 found a significant association between obesity and overall survival among patients with pancreatic cancer. The article did not discuss chronic medication use by the participants, and it is possible that insulin, insulin secretagogues, metformin, and statin therapy might have confounded this relationship.
Obese individuals are more likely to be treated chronically with antidiabetic drugs and statins because of their metabolic abnormalities. Although in vitro data suggest that statins might decrease pancreatic cancer cell invasion and metastasis,2 clinical trial data suggest that chronic statin therapy may increase cancer incidence, particularly in elderly persons.3 This might result from a statin-induced increase in regulatory T-cell numbers and functionality, leading to an impairment of host antitumor response and increased cancer promotion.4 Additionally, in a recent case-control study, insulin or insulin secretagogue therapy was associated with an increased risk of pancreatic cancer, whereas metformin was associated with a decreased risk.5