Main Session
Sep
30
PQA 08 - Gastrointestinal Cancer, Nonmalignant Disease, Palliative Care
3416 - Impact of Preoperative Ablative Radiation after Induction Chemotherapy for Borderline Resectable Pancreatic Adenocarcinoma
Presenter(s)
Alden D'Souza, MD, MPHS - Washington University School of Medicine, Saint Louis, MO
A. D'Souza1, O. Sager1, K. J. Robbins1, B. Kalaghchi1, A. Mo1, C. J. DeSelm1, M. R. Waters1, E. Laugeman1, E. Morris1, T. Zhu1, X. Zhao1, P. Grierson2, D. Denardo1, R. Panni3, D. Sanford3, K. H. Lim1, and H. Kim1; 1WashU Medicine, Department of Radiation Oncology, St. Louis, MO, 2WashU Medicine, Division of Oncology, St. Louis, MO, 3WashU Medicine, Department of Surgery, St. Louis, MO
Purpose/Objective(s):
Online adaptive stereotactic body radiotherapy (SBRT) for pancreatic adenocarcinoma enables safe delivery of ablative doses without prolonged fractionation. We evaluated oncologic outcomes and postoperative complications of patients with borderline resectable pancreatic cancer (BRPC) who received induction chemotherapy plus adaptive SBRT (IC-RT) versus induction chemotherapy alone (IC alone) prior to resection.Materials/Methods:
Patients with BRPC treated at a single institution with preoperative IC-RT vs IC alone were propensity matched by age, gender, vascular involvement, and gastrointestinal organ involvement using nearest neighbor method. Patients in the IC-RT cohort received online adaptive SBRT (50 Gy in 5 fractions). Progression free survival (PFS) and overall survival (OS) were calculated using the Kaplan-Meier method, and factors associated with outcomes of interest were evaluated using Cox regression analyses. Oncologic outcomes were measured from the time of initial diagnosis.Results:
Patients underwent resection from 2015-2020 (IC-alone) and 2021-2024 (IC-RT). One-to-one propensity matching for 143 treated patients resulted in 23 patients in each cohort. Median age at diagnosis was 66 years (range: 47-78). Most tumors were in the pancreatic head, neck, or uncinate (76%) and abutted at least one gastrointestinal luminal organ (96%). Patients in the IC alone vs IC-RT cohort received FOLFIRINOX (52% vs 61%), gemcitabine (39% vs 22%), or both (9% vs 13%), with a median of 5 vs 8 cycles prior to resection, respectively. There were 20 (87%) and 8 (35%) patients with arterial involvement in the IC-RT and IC alone cohorts, respectively. The adapted plan was used in 112/115 fractions (97%). Non-adapted plans exceeded duodenum, stomach, small bowel and large bowel constraints in 72 (63%), 67 (58%), 59 (51%) and 25 (22%) fractions, respectively. R0 resection rate was 17 (74%) and 13 (57%) in the IC-RT and IC alone cohorts, respectively (p=0.22). PFS at 1-, 2-, 3-years for IC-RT vs IC alone cohorts was 87% vs 65%, 47% vs 30%, and 31% vs 22%, respectively (p=0.22). OS at 1-, 2-, 3-years for IC-RT vs IC alone cohorts was 96% vs 65%, 57% vs 52%, 42% vs 26%, respectively (p=0.32). There were 4 (17%) grade 3 or higher postoperative complications in the IC-RT cohort and 7 (30%) in the IC alone cohort (p=0.30).Conclusion:
Preoperative adaptive SBRT with ablative dosing after induction chemotherapy (IC-RT) for patients with BRPC results in promising R0 resection rates, PFS and OS without increasing postoperative complications compared to IC alone. Larger patient cohort studies may determine if there are significant differences between these treatment paradigms.