Stereotactic Body Radiation Therapy is Safe and Feasible for the Treatment of Locally Recurrent Pancreatic Adenocarcinoma after Curative Resection

Abstract

<h3>Purpose/Objective(s)</h3> Locoregional relapse rates following surgical resection of pancreatic cancer can be as high as 45-50%. The majority of these patients are not candidates for re-resection due to co-morbidities and/or technically unresectable disease, highlighting the role of non-invasive options such as radiation therapy. The purpose of this study was to report on a cohort of radiation-naïve patients who developed isolated local recurrence following surgical resection and were subsequently treated with stereotactic body radiation therapy (SBRT). <h3>Materials/Methods</h3> Patients who were treated with SBRT for locally recurrent pancreatic cancer after initial curative resection were retrospectively reviewed. Clinical outcomes were calculated from completion of SBRT and included overall survival (OS), local progression-free survival (LPFS), distant metastasis-free survival (DMFS), and progression-free survival (PFS). Univariate and multivariate analyses were performed to identify variables associated with clinical outcomes. Kaplan-Meier analysis was performed for survival outcomes. Toxicity was assessed using the Common Terminology Criteria for Adverse Events version 4.0. <h3>Results</h3> From September 2012 to November 2018, a total of 19 patients were treated with SBRT for locally recurrent pancreatic cancer after initial surgical resection. No patients had prior radiation. The most common SBRT dose/fractionation was 33 Gy in 5 fractions (12/19, 63.1 %), followed by 25 Gy in 5 fractions (4/19, 21.0%), 28 Gy in 5 fractions (1/19, 5.3%), 27 Gy in 4 fractions (1/19, 5.3%), and 26.4 Gy in 4 fractions (1/19, 5.3%). Peri-SBRT chemotherapy was administered to 10 patients, in the pre-SBRT (3/19, 15.7%) and/or post-SBRT (8/19, 42.1%) setting. Median OS was 17.1 months, with 6-month and 1-year OS rates of 94.4% and 69.6%, respectively. A total of 9 patients (47.4%) developed local failure after SBRT. Pattern of first failure after SBRT was distant in 7 patients (46.7%), local in 5 patients (33.3%), and synchronous distant and local in 3 patients (20.0%). One patient developed local failure after developing distant disease first. Of the 9 local failures, 3 (33.3%) were out-of-field, involving the porta hepatis (n=1), pancreaticojejunostomy (n=1), and pancreatic remnant (n=1). Median LPFS was 22.2 months, with 6-month and 1-year LPFS rates of 86.9% and 63.2%, respectively. A biologically effective dose (BED₁₀) < 54.8 Gy was associated with inferior LPFS (1-year LPFS, 25.0% vs 80.2%, p<0.009). Median DMFS and PFS were 15.6 months. There was 1 case (5.3 %) of grade 3 gastric perforation. There were no cases of grade 4-5 toxicity events. <h3>Conclusion</h3> Stereotactic body radiation therapy for local recurrence after initial curative resection is safe and feasible. A BED₁₀ < 54.8 Gy was significantly associated with inferior local control, and one-third of local failures were out-of-field. Further studies investigating dose escalation and optimal treatment volumes in the locally recurrent setting are warranted.