Stereotactic body radiotherapy (SBRT) in recurrent or oligometastatic pancreatic cancer : Atoxicity review of simultaneous integrated protection (SIP) versus conventional SBRT.

Abstract

Stereotactic body radiotherapy (SBRT) in pancreatic cancer can be limited by its proximity to organs at risk (OAR). In this analysis, we evaluated the toxicity and efficacy of two different treatment approaches in patients with locally recurrent or oligometastatic pancreatic cancer. According to the prescription method, patients were divided in two cohorts (C1 and C2). The planning target volume (PTV) was created through a4 mm expansion of the internal target volume. In C2, asubvolume was additionally created, asimultaneous integrated protection (SIP), which is the overlap of the PTV with the planning risk volume of an OAR to which we prescribed areduced dose. In all, 18patients were treated (7 with local recurrences, 9 for oligometastases, 2 for both). Twelve of 23lesions were treated without SIP (C1) and 11 with SIP (C2). The median follow-up was 12.8months. Median overall survival (OS) was 13.2 (95% confidence interval [CI] 9.8-14.6) months. The OS rates at 6 and 12months were 87 and 58%, respectively. Freedom from local progression for combined cohorts at 6 and 12months was 93 and 67% (95% CI 15-36), respectively. Local control was not statistically different between the two groups. One patient in C2 experienced grade ≥3 acute toxicities and 1patient in C1 experienced agrade ≥3 late toxicity. The SIP approach is auseful prescription method for abdominal SBRT with afavorable toxicity profile which does not compromise local control and overall survival despite dose sacrifices in small subvolumes.