Clinical effect of intraoperative electron beam radiotherapy in treatment of unresectable locally advanced pancreatic cancer

Abstract

Objective To assess the prognostic benefits of intraoperative radiotherapy (IORT) with electron beam among patients with unresectable locally advanced pancreatic cancer. Methods Between January 2009 and December 2014, 167 patients with unresectable locally advanced pancreatic cancer received IORT with electron beam (10-20 Gy) in our hospital. After surgery, 12 patients were treated with external beam radiotherapy, 56 patients with chemoradiotherapy (CRT), and 17 patients with chemotherapy. Overall survival (OS), local recurrence, and toxicities were retrospectively analyzed. The Kaplan-Meier method was used to calculate survival rates, the log-rank test was used for survival difference analysis and univariate prognostic analysis, and the Cox model was used for multivariate prognostic analysis. Results The follow-up rate was 100%. The median OS time was 10.3 months, and the 2-year OS rate was 22%. The median progression-free survival (PFS) time was 6.3 months, and the 2-year PFS rate was 9.9%. The cancer-specific survival (CSS) time was 11.2 months, and the 2-year CSS rate was 23.6%. In the patients treated with IORT alone at doses of 15 Gy, the median OS times were 6.2 months vs. 9.1 months vs. 22.2 months, and the 1-year OS rates were 10.0% vs. 39.6% vs. 74.4%(P=0.000). Among the patients receiving postoperative adjuvant therapy, those treated with IORT+ CRT had the best survival, with a median OS time of 11.6 months (P=0.033). The univariate analysis showed that IORT dose (P=0.000), tumor size (P=0.006), and IORT applicator diameter (P=0.007) were prognostic factors. The multivariate analysis showed that IORT dose (P=0.000) and IORT combined with CRT (P=0.006) were independent prognostic factors. Conclusions IORT with electron beam is an effective and safe treatment strategy for unresectable locally advanced pancreatic cancer. After protecting surrounding organs, increasing the IORT dose can improve the survival. IORT combined with CRT should be recommended because it improves survival for unresectable locally advanced pancreatic cancer without increasing toxicities. Key words: Pancreatic neoplasms/intraoperative radiotherapy; Intraoperative radiotherapy, electron beam; Pancreatic neoplasms/postoperative radiochemotherapy; Prognosis