A matched pair analysis of five-fraction stereotactic body radiation therapy versus protracted conventional radiation therapy in patients receiving chemotherapy for locally advanced pancreatic cancer.

Abstract

444 Background: Stereotactic body radiation therapy (SBRT) is a novel treatment modality for unresectable, locally advanced pancreatic cancer (LAPC). SBRT delivers high doses of radiation over a shorter duration, with minimal acute toxicities, compared with conventional radiation therapy (CRT) using intensity modulated radiation therapy (IMRT) or 3D conformal techniques (3D-CRT). Few studies have compared outcomes between SBRT and CRT techniques. We conducted a retrospective matched pair analysis of LAPC patients receiving chemotherapy and either SBRT or CRT to assess local control (LC), progression-free survival (PFS), and overall survival (OS). Methods: We retrospectively analyzed 28 patients with LAPC who were treated between August 2006 and August 2014 with 5-FU- or gemcitabine-based chemotherapy combined with CRT (45–56 Gy over 25–28 fractions) or SBRT (25–30 Gy over 5 fractions). Fourteen patients treated with CRT were matched with 14 patients treated with SBRT for age (< 65 vs. ≥ 65 years); nodal staging (N0 or N1); and chemotherapy type (gemcitabine-based or 5-FU-based, administered either concurrently or as induction therapy). Tumor response was assessed using RECIST and all outcomes were calculated from the date of diagnosis. The Log Rank test of Kaplan-Meier curves was used for statistical analyses. Results: Median follow-up time was 11 months (mo). The median duration of LC, PFS, and OS for the entire cohort was 11, 8, and 14 mo, respectively. Median duration of LC was 10 mo for CRT and 11 mo for SBRT (p > 0.05). Median PFS was 8 mo for both groups (p > 0.05). The median OS times were 12 mo for SBRT and 16 mo for 3D-CRT/IMRT (p > 0.05). Conclusions: In this small matched-pair analysis, LAPC patients treated with chemotherapy had similar outcomes following 5 fractions of SBRT as compared with a protracted course of CRT. Given the shorter treatment duration with SBRT, further study is warranted with increased cohort sizes and stratification by other patient and disease characteristics.