672 patients with acinar cell carcinoma of the pancreas: a population-based comparison to pancreatic adenocarcinoma.

BACKGROUND: Acinar cell carcinoma (ACC) is a rare cancer of the pancreas accounting for approximately 1% of nonendocrine tumors. Because no large series of patients with ACC exist, our understanding of this disease comes mainly from small retrospective reports and anecdotal experience.
OBJECTIVE: Our goal was to evaluate a large population-based cohort of patients with ACC and compare their demographic factors and outcomes to those of patients with pancreatic adenocarcinoma (PA).
METHODS: Using the Surveillance, Epidemiology, and End Results (SEER) database (1988 to 2003), we identified all patients with ACC or PA. The demographic factors, tumor characteristics, resection status, and long-term survival were compared between the 2 groups.
RESULTS: A total of 672 patients with ACC and 58,526 with PA were identified. The mean age at the time of diagnosis was significantly lower for ACC than PA (56 years vs 70 years, P < .001). Compared with patients with PA, patients with ACC were more likely to be male (54% vs 48%, P = .007) and white (85% vs 81%, P = .03). Based on SEER clinical staging, patients with ACC were less likely to have unstaged disease (8% vs 18%). Of the 616 patients with staged ACC, 16% had localized disease, 26% had regional disease, and 58% had distant disease. In the 47,896 staged patients with PA, 10% had localized disease, 33% had regional disease, and 57% had distant disease (P < .0001 compared to ACC). Based on clinical extent of disease, 81% of patients with locoregional ACC and 70% of patients with locoregional PA were resectable. However, only 69% of ACC patients with locoregional disease and 27% of PA patients with locoregional disease underwent surgical resection. The overall 5-year survival was 42.8% for ACC (median, 47 months) and 3.8% for PA (median, 4 months, P < .0001). Patients with unresected ACC had a 5-year survival rate of 22% compared to 2% in patients with unresected PA (P < .0001). Surgical resection significantly improved survival. The 5-year survival was 72% in resected ACC and 16.3% in resected PA (P < .0001). Multivariate Cox proportional hazards regression model results suggested patients with ACC were less likely to die (hazard ratio = 0.241; 95% confidence interval, 0.22-0.27) than patients with PA after controlling for gender, race, stage, SEER region of diagnosis, and surgical resection status.
CONCLUSIONS: Consistent with anecdotal reports and previous retrospective studies, ACC is a more indolent disease than PA. Patients with ACC tend to present at a younger age, are more likely to have resectable disease, and are much more likely to undergo potentially curative resection. The long-term survival for patients with ACC is significantly better when compared to the long-term survival of patients with PA.