The combination of a cancer vaccine, pembrolizumab, and stereotactic body radiation in patients with locally advanced pancreatic cancer: a single-arm, phase II study

In this Phase II study (NCT02648282) of locally advanced pancreatic cancer (LAPC), 58 patients were enrolled and intended for an immunotherapy including GM-CSF-secreting allogeneic pancreatic cancer vaccine (GVAX) and pembrolizumab and stereotactic body radiation therapy (SBRT) following standard chemotherapy. Fifty-four evaluable patients received two cycles of immunotherapy and SBRT and reassessed for resectability. After resection or biopsy, patients received continued immunotherapy for two years. At a median follow-up of 19.6 months, the median distant metastasis free survival (DMFS), the primary endpoint, for all evaluable patients was 9.8 months. Secondary endpoint analysis shows that, of these, 35 patients (64.8%) were deemed potentially resectable, and 24 underwent R0/R1 resections. Resected patients had a majority of R0 resections (91.7%). The overall resection rate was 44.4%. Patients who underwent resection had a median DMFS of 20.3 months. Median overall survival (OS), a secondary endpoint, for all evaluable patients from the start of the immunotherapy was 21.8 months, with resected patients reaching 29.7 months and unresected patients at 12.1 months. From diagnosis, median OS was 28.2 months, with resected patients achieving 36.7 months, while unresected patients had 19.7 months. In conclusion, the combination of GVAX, pembrolizumab, and SBRT showed promising efficacy in LAPC patients with favorable survival outcomes, especially those who underwent R0/R1 resections. However, patients with unresectable disease still maintained significantly worse DMFS and OS. The regimen demonstrated a manageable safety profile.