PANCREATITIS AND PANCREATIC-CANCER - A POPULATION-BASED STUDY

Background: Little is known about the etiology of cancer of the exocri ne portion of the pancreas, which produces a variety of digestive enzy mes. Smoking, certain dietary factors, and diabetes mellitus are consi dered to be risk factors, although the risk estimates are modest in mo st instances. A recent cohort study of patients with chronic pancreati tis indicated a ninefold to 16-fold increased risk for pancreatic canc er. Purpose: Our purpose was to evaluate the relationship between vari ous clinical types of pancreatitis and pancreatic cancer. Methods: Dat a for this study were collected from all inpatient medical institution s in Sweden from 1965 until 1983 by the Swedish National Board of Heal th and Welfare. Data were recorded on individual hospital admissions a nd discharges in the Inpatient Register. All patients with records in the Inpatient Register coded for acute, chronic, or unspecified pancre atitis were considered for inclusion in the study. A population-based cohort of 7956 patients with at least one discharge diagnosis of pancr eatitis was monitored (up to 19 years of follow-up) for the occurrence of pancreatic cancer by record linkages to the Swedish Cancer Registr y and Registry of Causes of Death. Results: A total of 46 pancreatic c ancers were diagnosed during followup compared with 21 expected (stand ardized incidence ratio [SIR] of 2.2; 95% confidence interval [CI] 1.6 -2.9) for the Uppsala Health Care Region. The excess risk for women an d men was similar-most pronounced during the first period of follow-up (2-4 years) after discharge and close to unity after more than 10 yea rs of follow-up. Patients with chronic pancreatitis and patients with more than one discharge diagnosis of either acute or unspecified pancr eatitis were at higher risk (SIR = 3.8; 95% CI 1.4-8.2 and SIR = 4.8; 95% CI 1.9-9.9, respectively) compared with those with only one discha rge of acute (SIR = 1.6; 95% CI 0.9-2.7) or unspecified (SIR = 2.1; 95 % CI 1.2-3.2) pancreatitis. Conclusions: Our finding of a moderate exc ess of pancreatic cancer among patients with pancreatitis, especially the chronic or recurrent forms, supports some earlier clinical and cas e-control studies, but it is not consistent with the ninefold to 16-fo ld risk reported in a recent cohort study. The absence of an increased risk 10 years or more after first discharge for pancreatitis argues a gainst a straightforward causal relationship. Because of the relativel y short interval between diagnosis of pancreatitis and pancreatic canc er, it is possible that some forms of pancreatitis are a precursor to pancreatic cancer or that shared risk factors for both diseases (e.g., cigarette smoking) may also be involved.