The Diabetes-Pancreatic Cancer Risk Relationship over Time: A Systematic Review and Meta-Analysis

Background/Objectives: The relationship between diabetes and pancreatic cancer (PCa) is controversial. In this meta-analysis and systematic review, we investigated diabetes and time since diagnosis as risk factors for PCa. Methods: Cohort and case-control studies were retrieved through a literature search. RevMan 5.4 software and a random effects model were used to estimate summary risks with their 95% confidence intervals (CIs), and the Newcastle–Ottawa Scale (NOS) was used to assess study quality. Results: Included were 23 studies representing 30,875,355 participants and 86,980 cases of PCa. The summary risk for the 14 case-control studies was 2.30 (95% CI: 2.03–2.62) and for the 9 cohort studies was 2.39 (95% CI: 2.09–2.73). The risk decreased with time after diabetes diagnosis: 3.27, 2.25, 1.55, and 1.12 for <2, 2–5, 5–10, and >10 years, respectively, in the case-control studies. The cohort studies also showed an increased risk of PCa in the first 2 years (4.29) and a decrease over time. Quality scores according to the NOS were 6–9 (good and fair quality), for an overall average of 7.82. Conclusions: Diabetes is a risk factor for PCa and this risk is much higher in the 2 years following diabetes diagnosis. In this period, the subgroup of patients who, through clinical follow-up and/or cancer screening, would have better clinical outcomes should be identified. Bearing in mind the poor survival rate for PCa, diabetes interventions focused on preventing onset and delaying progression via modifiable risk factors to reduce PCa incidence.