An exploratory phase I trial of immunochemoradiotherapy in locally advanced and borderline resectable (LA/BR) pancreatic adenocarcinoma (PC).

Abstract

174 Background: The primary aim of this exploratory trial was to determine the feasibility and safety of chemoradiotherapy (CRT) with combinatorial immunotherapy in LA or BR PC. Methods: 10 patients (pts) with untreated, LA (n=6) or BR (n=4) biopsy-proven PC received gemcitabine (GEM) in combination with telomerase peptide vaccine (GV1001) and sargramostim (GM-CSF) both by intradermal injection. Tadalafil was taken once daily throughout the course of therapy for myeloid derived suppressor cell inhibition. The 2nd month of treatment included external beam radiation therapy (50.4 Gy, 28 fractions) and concurrent twice-weekly GEM 50 mg/m2. Disease response was assessed at 12 weeks. Following recovery from either concurrent CRT or resection, 8 weeks of GV1001 + GM-CSF, tadalafil and GEM completed treatment. Peripheral blood was analyzed by quantitative multiparameter whole blood flow cytometry of immune cell subtypes. Samples were also cryo-preserved for future analysis of peripheral blood mononuclear cell (PBMC) populations and ELISPOT analysis of antigen-specific T cell numbers. Tumor resection specimens were sectioned for immunohistological analysis of macrophage and T cell infiltration. Results: 9 of 10 pts completed therapy to assess response. Grade (Gr) 3-4 hematologic adverse events (AE) were observed during CRT. Immune-related AE were infrequent and mild. 3 of 4 pts with BR disease and 1 with initial LA (unresectable) disease achieved R0 resection. No unanticipated surgical complications were observed. Changes in monocytes and granulocytes occurred throughout treatment and may correlate with clinical benefit. At least 50% reduction in serum CA19-9 was observed in 8 pts. Partial response (n=2) or stable disease (n=7) was achieved in 9 pts. Conclusions: Combinatorial immunotherapy concurrent with GEM-based CRT is feasible and appears safe in LA or BR PC. Initial biochemical responses as well as disease control were observed in the majority of pts. Preliminary immune correlative data suggest a relationship between hematopoietic populations and clinical response.