Optimal Target Volume Delineation for Pancreatic Cancer: Triangulating What Should be Targeted.

Optimal target volume delineation for pancreatic cancer remains an unanswered question across all stages of disease. To-date, target volume delineation has been highly variable across major clinical trials that have explored the role of radiation for this disease, which undoubtedly has contributed to the significant variation in outcomes that have been observed between such trials and the current controversy that has therefore been generated surrounding the role of radiation for pancreatic cancer. Importantly, emerging data has increasingly suggested that elective volume targeting is critical for this disease and that volume delineation should be driven by those patterns of locoregional spread that drive locoregional failure, namely extra-pancreatic perineural invasion. Herein, we review the historical approaches that have been used for target volume delineation across key studies to-date as well as recent data that provide critical insights into optimal target volume delineation in the setting of radiation for pancreatic cancer.