New diagnosis of chronic pancreatitis: risk of missing an underlying pancreatic cancer.

OBJECTIVES: Patients with pancreatic cancer (PaCa) sometimes present with symptoms suggestive of chronic pancreatitis (CP). We evaluated the prevalence of undiagnosed PaCa in patients with new CP diagnosis.

METHODS: This is a retrospective study with data from Veterans Health Administration national medical care data sets from fiscal year 1998-2007. A 3-year washout period was used to identify patients with preexisting PaCa and preexisting CP diagnosis.

RESULTS: Among 471,992 veterans included, 917 (0.19%) had PaCa, 2,557 (0.54%) had a preexisting CP, and 2,175 (0.46%) had a new diagnosis of CP. PaCa was diagnosed ≤2 years following CP diagnosis in 44 patients, comprising 4.80% of patients with PaCa. Following a new diagnosis of CP, the risk of PaCa diagnosis was most marked in the first year (incidence 18.04 per 1,000 person-years (py), relative risk (RR) 63.43) and became similar to risk in patients with preexisting CP in the third year. The first-year incidence of PaCa was 7.33/1,000 py in the fifth decade and reached 36.91/1,000 py after seventh decade of life. Time to PaCa diagnosis following a CP diagnosis was ≤60 days in 14 patients, 3-12 months in 25 patients, and 13-24 months in 5 patients.

CONCLUSIONS: Approximately 5% of patients with PaCa are initially misdiagnosed as CP, and in two-thirds of these patients the cancer diagnosis is delayed by >2 months. PaCa should reliably be excluded before making a new CP diagnosis in patients who are >40 years old, especially in those without heavy smoking or alcohol history.