Pancreatic Cancer: "A Riddle Wrapped in a Mystery inside an Enigma".

Pancreatic ductal adenocarcinoma (PDAC) is one of the most difficult-to-treat cancers. With an increasing incidence and inability to make major progress, it represents the very definition of unmet medical need. Progress has been made in understanding the basic biology-systematic genomic sequencing has led to the recognition that PDAC is not typically a heavily mutated tumor, although there are exceptions. The most consistently mutated genes are KRAS, CDKN2A, TP53, and SMAD4/DPC4 Study of familial PDAC has led to the recognition that a variety of defects in DNA repair genes can be associated with the emergence of pancreatic cancer. Recent studies suggest that epigenetics may play a larger role than previously recognized. A major new understanding is the recognition that PDAC should be considered a composite of tumor cells, as well as pancreatic stellate cells, immune cells, and extracellular matrix. The individual components contribute to metabolic aberration, immune dysfunction, and chemotherapy resistance, and therapeutic innovations may be needed to address them individually. It has also been recognized that metastatic seeding from PDAC occurs very early in the disease course-in an estimated 73% of cases, once the tumor reaches 2 cm. The implication of this is that therapies directed toward micrometastatic disease and increasing fractional cell kill are most needed. Neoadjuvant approaches have been taken to increase resectability and improve outcome. So much work remains, and most critical is the need to understand how this tumor originates and develops. Clin Cancer Res; 23(7); 1629-37. ©2017 AACRSee all articles in this CCR Focus section, "Pancreatic Cancer: Challenge and Inspiration." ©2017 American Association for Cancer Research.