Effect of chemoradiation-related lymphopenia on survival in patients with unresectable, locally advanced pancreatic adenocarcinoma

307 Background: Pancreatic ductal adenocarcinoma (PDA) has been shown to elicit antitumor cell-mediated immune responses. In high grade gliomas, treatment-related lymphopenia has been associated with shorter survival. This study was performed to determine if patients with locally advanced PDA treated with definitive chemoradiation therapy (CRT) develop significant lymphopenia and if this affects overall survival (OS). Methods: A retrospective analysis of patients with locally advanced PDA treated at a single institution with CRT from 1997-2009 was performed. Serial lymphocyte counts were recorded and OS was analyzed as a function of lymphopenia and known prognostic factors. Results: 99 patients met eligibility criteria (≥18 years of age, ECOG performance status 0-2, and had baseline/follow-up lab values measured at our institution). Mean age was 61.6 years (SD, 11.6), 55% were male, mean tumor size 4.1 cm (SD, 1.6), and 97 had stage III disease. Median pre/post-CRT CA19-9 values were 241.5 and 105.2 U/mL, respectively. Total lymphocyte counts were normal in 87% of patients prior to RT. Mean RT dose was 47.3 Gy (SD, 8.2) and concurrent chemotherapy was 5-FU (67%), gemcitabine (20%), taxotere (7%), or none (6%). Chemotherapy dose reduction was necessary in 9%, and 39% required a RT break. Total lymphocyte counts fell to ≤500 cells/mm3 in 51% two months after initiating CRT with a median reduction of 66% from baseline (p3 at 2 months was 7.7 months (95% CI, 6.8-8.7) versus 15.4 (95% CI, 11.9-19.0) for patients with >500 cells/mm3 (p3) at 2 months post-CRT (HR 3.8, p Conclusions: Definitive CRT induced lymphopenia is frequent, severe, and appears to be an independent predictor for OS in patients with locally advanced PDA.