Intensity-modulated radiation therapy (IMRT) in patients with locally advanced pancreatic cancer (LAPC).

Abstract

377 Background: To assess IMRT safety and evaluate local control and resectability among patients with LAPC treated with induction CT followed by IMRT. Methods: We reviewed records of 134 LAPC patients treated with CT (median duration 3.2 months) followed by IMRT (median dose 56 Gy) between 11/2006 and 11/2012. Patients had LAPC based on T4 disease or unreconstructable involvement of portal vein/hepatic artery on imaging (n=102) or were found to be unresectable after an attempted resection (n=32). Induction CT was gemcitabine-based (n=98) or FOLFIRINOX (n=32); concurrent CT was gemcitabine in 88 patients, continuous 5-FU or capecitabine in 37 patients. IMRT was given after induction CT in the absence of evidence of disease progression. After IMRT, 81 patients received maintenance CT. Results: Acute grade 3 GI and hematologic toxicity were seen in 4 (2.9%) and 33 (24.6%) patients, respectively. Acute grade 4 GI and hematologic toxicity were seen in 0 and 5 (3.7%) patients, respectively. Ten patients (7.4%) developed late grade 1 GI toxicity and 2 patients (0.7%) developed compression fractures. Twenty-six (19.4%) patients underwent resection 4.1 months (mean) after IMRT; 22 (84.6%) had negative margins, one of whom had a pathologic complete response and 4 had a microscopically positive margin. With 20.1 months median f-up, median local progression-free survival (LPFS) was 17.6 months. One- and 2-year LPFS were 90% and 55% respectively. Median distant metastasis free survival (DMFS) was 15.2 months. One- and 2-year DMFS were 69.5% and 30.7% respectively. Median OS was 19.7 months for the whole population (24.8 months for surgical patients and 19.7 months for the non-surgical patients). One- and 2-year OS for all patients were 85% and 47% respectively; one- and 2-year OS for the surgical patients were 96% and 72% respectively. Conclusions: In this large cohort of patients treated with IMRT for LAPC, acute and late toxicity was minimal. Patients with non-progressive LAPC after induction CT who received IMRT had high rates of local control which could translate into a better quality of life. In selected patients, induction CT followed by IMRT can downstage tumors allowing for R0 resections and improved overall survival.