Patterns of failure in a phase II trial of neoadjuvant chemotherapy and stereotactic body radiation therapy (SBRT) for resectable and borderline resectable (BLR) pancreatic cancer.

482Background: There is emerging interest in the role of SBRT in locally advanced pancreas cancer, however little prospective data exists examining the safety, efficacy, and optimal target volumes for SBRT in the neoadjuvant setting for resectable or BLR pancreatic cancer. Methods: Eighteen patients were enrolled from 11/2014-6/2017. SBRT was delivered to the tumor and abutting vessel with fiducials/compression and a 3 mm PTV margin to 33 Gy (6.6 Gyx5fxn) with an optional elective PTV to 25 Gy (5 Gyx5fxn) customized to the nodal space and mesenteric vessels. Patients without progression underwent surgery 4-6 weeks following SBRT. The primary endpoint is ≥ Grade 3 acute and late GI toxicity. Secondary endpoints included overall survival (OS), progression-free survival (PFS),and cumulative incidence of local failure (LF). LF is defined as recurrence within conventional RT volumes from the time of resection to local failure or last CT with no progression. Local failures were fused to planning CTs for dose qu...