New-onset diabetes in pancreatic cancer: A study in the primary care setting

Background: Onset of diabetes mellitus (DM) is often first noted by primary care physicians. New-onset DM (duration <36 months before PaC diagnosis) can be a harbinger of pancreatic cancer (PaC). However, its clinical significance remains unclear. Methods: To determine the prevalence, onset, and delay in diagnosis of DM in PaC patients in the primary care setting, we retrospectively reviewed the records of consecutive patients followed in Mayo Clinic's primary care clinics (at least one visit in the preceding 2 years) from 1995 to 2009 who were eventually diagnosed with PaC. Onset of DM was the first date the fasting blood glucose was ≥126 mg/dl. Results: Of the 111 PaC patients (59 male, median age 74 years), 52 (47%) had DM of whom 30 (58%) had new-onset DM. Among the 30 with new-onset DM, 24 (80%) were asymptomatic (no cancer-specific symptoms), at DM onset. In these 24 patients, median duration of DM prior to PaC diagnosis was 6.5 (0.5-35) months, and median delay between onset and physician diagnosis of DM was 2.5 (0.25-14) months, which decreased from 8.8 (3.5-14) months in patients with DM onset between 1995 and 1999 to 0 (0-2) months, in patients with DM onset between 2004 and 2009. However, the proportion of patients with undiagnosed DM (∼33%) remained unchanged. Conclusions: Diabetes is very common (∼50%) in PaC. In over a fifth of PaC, the onset of DM occurs when the cancer is asymptomatic, providing a potential window-of-opportunity to diagnose early PaC. However, nearly a third of new-onset DM in PaC remains undiagnosed.