2008 Annual Meeting Abstracts

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Background: Pancreatic acinar cell carcinoma (ACC) is a rare tumor with poorly defined risk and prognostic factors. Our objective was to compare a large population of ACC to pancreatic adenocarcinoma in order to assess factors predicting ACC, assess differences in survival, and identify prognostic factors.
Methods: From the National Cancer Data Base (NCDB), patients with pancreatic ACC and adenocarcinoma were identified. Multiple logistic regression was used to assess differences between ACC and adenocarcinoma. Median follow-up in resected patients was 22 months. 5-year overall survival was estimated by Kaplan-Meier method and compared using log-rank tests. Cox proportional hazards modeling was used to identify predictors of survival in resected patients.
Results: 865 patients with ACC were identified (Stage I: 14.1%, II: 20.5%, III: 11.6%, IV: 33.5%, unknown 20.2%). Median age at diagnosis was 67 yrs. Tumors were located in the head of the pancreas 42.3%, body 7.6%, tail 19.8%, and diffuse/NOS 30.3%. Of the 333 who underwent resection, 62% underwent surgery alone, 17% received chemotherapy, 7% received radiation, and 26.8% underwent chemoradiation. Median tumor size was 6.9 cm (vs.4.6 cm for adenocarcinoma). 32.1% had nodal metastases (vs.48.0% for adenocarcinoma). 47% had high-grade tumors (vs.37.3% for adenocarcinoma). Resection margins were R0 in 77.3%, R1 in 13.7%, and R2 in 9.0%. Patients underwent resection at NCI centers 12.3%, other academic hospitals 34.2%, VA facilities 1.2%, and community hospitals 52.2%. Patients were more likely to have ACC if male, white, larger tumor size, no nodal involvement, or pancreatic tail tumors. Five-year survival in resected patients was significantly better than in patients who did not undergo resection: 36.2%vs.10.4%. Stage-specific survival was significantly better for resected ACC vs. adenocarcinoma: I: 52.4%vs.28.4%, II: 40.2%vs.9.8%, III: 22.8%vs.6.8%, and IV: 17.2%vs.2.8%. On univariate analysis, age <65 yrs, well-differentiated tumors, R0 status, and adjuvant chemoradiation were associated with better long-term survival. On multivariate analysis, age <65, well-differentiated tumors, and negative margins (R0 vs. R1/R2) were the only independent prognostic factors.
Conclusions: ACC accounts for ~1% of resected pancreatic cancers; however, it carries a considerably better prognosis than pancreatic adenocarcinoma. Tumors are typically larger, but size is not associated with survival and should not preclude resection. Thus, surgical resection with negative margins and consideration of adjuvant therapy is the best chance for long-term survival in these favorable pancreatic cancers.

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