Phase 1 Study of Adjuvant Allogeneic Granulocyte-Macrophage Colony-Stimulating Factor-Transduced Pancreatic Tumor Cell Vaccine, Low-Dose Cyclophosphamide, and Stereotactic Body Radiation Therapy Followed by FOLFIRINOX in High-Risk Resected Pancreatic Ductal Adenocarcinoma

Purpose: Local and distant progression remains common following resection of resectable pancreatic ductal adenocarcinoma (PDAC) despite adjuvant multiagent chemotherapy. We report a prospective institutional phase 1 trial incorporating adjuvant GVAX vaccine, low-dose cyclophosphamide (Cy), and stereotactic body radiation therapy (SBRT) followed by FOLFIRINOX (FFX) among patients who underwent resection of high-risk PDAC. Patients and Methods: The study design was a modified 3+3. Cohort 1 received 5-fraction SBRT to 33 Gy to the tumor bed and 25 Gy to elective nodes followed by 6 cycles of full-dose FFX. After toxicity review, cohort 2 had SBRT and was switched to modified FFX (mFFX). Cohort 3 had 1 cycle of Cy/GVAX followed by SBRT, mFFX, and 4 cycles of maintenance Cy/ GVAX with 6-month Cy/GVAX boosts until progression. Results: Nineteen patients were enrolled with a median follow-up of 36.2 months. To be eligible, patients were required to have close/positive margins (within <= 1 mm) (71%) and/or lymph node metastasis (79%). Overall, 63% of patients had both. In cohort 1, 67% of patients received 6 cycles of FFX; in cohort 2, 75% received 6 cycles of modified FFX. In cohort 3, 12 patients received the first dose of Cy/GVAX and SBRT with 10 individuals (83%) receiving 6 cycles of mFFX. Cohort 3 had acceptable levels of grade >= 3 thrombocytopenia, neutropenia, and diarrhea after 2 cycles of mFFX. Median overall survival (OS)/diseasefree survival (DFS) for the overall cohort and cohort 3 was 36.2/18.2 months and 61.3/24.1 months, respectively. One- and 2year OS for cohort 3 was 83%/75%, respectively. At the last follow-up (median = x), 5 patients were alive (42%) in cohort 3. Conclusions: This is the first prospective trial to evaluate adjuvant GVAX, Cy, SBRT, and mFFX in resected PDAC patients with high-risk features. This combination regimen was well tolerated with limited toxicity and promising survival outcomes, warranting future studies to validate this regimen in the adjuvant setting. (c) 2024 Published by Elsevier Inc.