Abstract
Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related mortality in the United States, with poor overall survival across all stages. Less than 20% of patients are eligible for curative surgical resection at diagnosis, and despite adjuvant chemotherapy, most will experience disease recurrence within two years. The incorporation of immune-based strategies in the adjuvant setting remains an area of intense investigation with unrealized promise. It offers the potential of providing durable disease control for micro-metastatic disease following curative intent surgery and enabling personalized treatments based on mutational neoantigen profiles derived from resected specimens. However, most of these attempts have failed to demonstrate significant clinical success, likely due to the immunosuppressive tumor microenvironment (TME) and individual genetic heterogeneity. Despite these challenges, immune-based strategies, such as therapeutic vaccines targeted towards neoantigens, have demonstrated promise via immune activation and induction of T-cell tumor infiltration. In this review, we will highlight the foundational lessons learned from previous clinical trials of adjuvant immunotherapy, discussing the knowledge gained from analyses of trials with disappointing results. In addition, we will discuss how these data have been incorporated to design new agents and study concepts that are proving to be exciting in more recent trials, such as shared antigen vaccines and combination therapy with immune-checkpoint inhibitors and chemotherapy. This review will evaluate novel approaches in ongoing and future clinical studies and provide insight into how these immune-based strategies might evolve to address the unique challenges for treatment of PDAC in the adjuvant setting.