Multistate Model of the Natural History of Inflammatory Pancreatic Diseases: A Nationwide Population-based Cohort Study.

Background & Aims: Understanding the nature of inflammatory pancreatic diseases is essential for planning health care system requirements and interventions. The aim of this study was to quantify the trajectories of inflammatory pancreatic diseases and their association with pancreatic cancer in a population-based setting.

Methods: National health registries were used to identify all Danish residents (18 years or older) in the period from 2000 through 2018 with incident cases of acute pancreatitis (AP), recurrent acute pancreatitis (RAP), chronic pancreatitis (CP), and pancreatic cancer. We used a multistate model to examine transitions from a healthy state to intermediate states of acute pancreatic inflammation (AP and RAP) to chronic states (CP and pancreatic cancer) and, ultimately, death. Results were reported as transition incidence rates per 1000 person-years with 95% CIs.

Results: There were 4,663,864 individuals included (mean age, 46 years; 51% were women). During a mean follow-up of 16.8 years, 31,396 individuals were diagnosed with incident AP, 5546 with RAP, 8898 with CP, and 18,182 with pancreatic cancer. The cumulative incidence of pancreatitis (acute and chronic) during the study period was 0.80% (95% CI, 0.79%-0.80%). The transition incidence rates to CP were 12.1 (95% CI, 8.1-18.1) from AP, 46.8 (95% CI, 31.6-69.3) from RAP, and 0.07 (95% CI, 0.04-0.13) from a healthy state. Similar patterns were observed for transitions to pancreatic cancer. Most patients diagnosed with CP (64.2%) and pancreatic cancer (96.4%) transitioned directly from a healthy state. Among patients with pancreatitis, 41.0% (95% CI, 40.5%-41.5%) died during follow-up.

Conclusions: The study findings revealed an increased risk of CP and pancreatic cancer in patients with a history of AP. However, most patients with CP and pancreatic cancer transitioned directly from a healthy state.