Advances in therapeutic vaccines for pancreatic cancer.

Pancreatic cancer is one of the most difficult-to-treat cancers. Despite surgical resection, radiation and/or chemotherapy, greater than 94% of people with pancreatic cancer do not survive beyond 5 years. In fact, median survival after diagnosis of metastatic pancreatic cancer is 4.5 months. The majority of patients are diagnosed with nonresectable, metastatic disease, and chemotherapy only extends their median survival by less than 2 months with only 18% of those treated surviving beyond 1 year. Despite the severity of their disease, most patients exhibit tumor specific cellular immunity to their pancreatic cancer antigens. Obviously their immunity is ineffective in preventing tumor growth. Recent studies have demonstrated that the tumor microenvironment may hold the key to determining the nature of the tumors' ability to escape from immune attack. Preliminary clinical trials have suggested that blocking these escape mechanisms may result in survival benefit to the patients, and phase I and II clinical trials with tumor vaccines have led to some survival benefits. Perhaps combining therapies directed against immune escape mechanisms with tumor vaccines will result in even greater survival benefit for patients with pancreatic cancer. While therapeutic vaccines for pancreatic cancers have been reviewed previously (Plate, 2011), updates on recent preliminary reports of two clinical vaccine trials are worthy of our attention.