Proton beam reirradiation for locally recurrent pancreatic adenocarcinoma.

BACKGROUND: Local recurrence following definitive treatment for pancreatic adenocarcinoma is common and can be associated with significant morbidity and mortality. Retreatment options for these patients are limited. Proton beam reirradiation (PRT) may limit dose and toxicity to previously irradiated normal tissues in patients without evidence of metastatic disease.

METHODS: Between 8/2010-2/2015, 15 patients with isolated, locally-recurrent pancreatic cancer were treated with PRT. Acute toxicity was graded using CTC v 4.0 and defined as occurring within 90 days. Kaplan-Meier survival analysis was performed from the start of PRT. A log-rank test was used to compare survival with or without concurrent chemotherapy.

RESULTS: Median follow-up was 15.7 months [2-48] from the start of PRT. The median clinical target volume (CTV) was 71 cc [15-200]. Ten (67%) patients received concurrent chemotherapy. Median PRT dose was 59.4 Gy (37.5-59.4 Gy). The median time interval from the prior treatment course was 26.7 months (7-461.3). There was a rate of 13% acute ≥ grade 3 toxicities attributed to PRT. The median overall survival (OS) was 16.7 months (95% CI, 4.7-36) and OS at 1 year was 67%. The "in-field" failure free survival at one year was 87%. The locoregional progression free survival (LPFS) and distant metastasis free survival (DMFS) at 1 year was 72% and 64% respectively. Concurrent chemotherapy was associated with a higher median survival.

CONCLUSIONS: PRT was well tolerated, resulted in prolonged clinical outcomes compared to historical controls, and should be considered as a treatment option with concurrent chemotherapy in selected patients with locally-recurrent pancreatic cancer.