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Pancreatitis and pancreatic cancer: a population-based study.

BACKGROUND
Little is known about the etiology of cancer of the exocrine portion of the pancreas, which produces a variety of digestive enzymes. Smoking, certain dietary factors, and diabetes mellitus are considered to be risk factors, although the risk estimates are modest in most instances. A recent cohort study of patients with chronic pancreatitis indicated a ninefold to 16-fold increased risk for pancreatic cancer.


PURPOSE
Our purpose was to evaluate the relationship between various clinical types of pancreatitis and pancreatic cancer.


METHODS
Data for this study were collected from all inpatient medical institutions in Sweden from 1965 until 1983 by the Swedish National Board of Health and Welfare. Data were recorded on individual hospital admissions and discharges in the Inpatient Register. All patients with records in the Inpatient Register coded for acute, chronic, or unspecified pancreatitis were considered for inclusion in the study. A population-based cohort of 7956 patients with at least one discharge diagnosis of pancreatitis was monitored (up to 19 years of follow-up) for the occurrence of pancreatic cancer by record linkages to the Swedish Cancer Registry and Registry of Causes of Death.


RESULTS
A total of 46 pancreatic cancers were diagnosed during follow-up compared with 21 expected (standardized 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 and 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 years of follow-up. Patients with chronic pancreatitis and patients with more than one discharge diagnosis of either acute or unspecified pancreatitis 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 discharge 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 excess of pancreatic cancer among patients with pancreatitis, especially the chronic or recurrent forms, supports some earlier clinical and case-control studies, but it is not consistent with the ninefold to 16-fold risk reported in a recent cohort study. The absence of an increased risk 10 years or more after first discharge for pancreatitis argues against a straight-forward causal relationship. Because of the relatively short interval between diagnosis of pancreatitis and pancreatic cancer, 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.