Adjuvant Stereotactic Body Radiotherapy for Resected Pancreatic Adenocarcinoma with Close or Positive Margins

The aim of this study was to evaluate the role of stereotactic body radiotherapy (SBRT) as adjuvant therapy for resected pancreatic adenocarcinoma with close or positive margins.

Between September 2006 and January 2010, 24 patients were treated with adjuvant SBRT following surgical resection. Eight (33.3%) patients had close margins of 1–2.5 mm to the retroperitoneal, vascular structures, and periduodenal adipose tissue. Sixteen (66.7%) patients had positive margins at retroperitoneal margin and vascular structures. Twenty-three patients received 24 Gy (20–24 Gy) in one fraction, and one had 30 Gy in three fractions. The median target volume was 11 cc (4.5–30 cc). Eighteen patients were treated with the Cyberknife® Robotic Radiosurgery System and six patients were treated with Trilogy™ intensity-modulated radiosurgery. Kaplan–Meier survival analyses were used to estimate freedom-from-local-progression (FFLP), and overall survival (OS) rates. PET/CT or CT was used to monitor disease recurrence following SBRT.

The median follow-up for all patients was 12.5 months (1.4–39.5 months), and among surviving patients it was 16.3 months (2–39.5 months). The FFLP rates at 6 months, 1 and 2 years were 94.7%, 66%, and 44%, respectively. Overall, FFLP was achieved in seven (87.5%) patients with close margins, and 10 (62.5%) with positive margins. After SBRT, 19 patients resumed or started a 6-month course of gemcitabine-based chemotherapy at a median interval of 18 days (range, 9–31 days) post-SBRT. The median OS was 26.7 months and the 1- and 2-year OS rates were 80.4% and 57.2%, respectively. Of the 24 patients, 12 (50%) developed distant metastases of whom two (25%) had close margins and 10 (62.5%) had positive margins. Ten patients (41.7%) were free of progression at last follow-up (range, 3–39.5 months). Three patients (12.5%) had grade 1–2 acute GI toxicities, and two patients (8.3%) had grade 1 and 2 late toxicities. No patients experienced grade 3 or 4 toxicity, including bowel perforation, secondary to SBRT.

Our data suggest that adjuvant SBRT for resected pancreatic cancer can be achieved with minimal toxicity. This shorter treatment course allowed initiation of systemic chemotherapy shortly after the completion of SBRT.