Therapeutic anti-cancer vaccines developed to treat metastatic disease such as advanced prostate cancer or melanoma don'thave a noticeable effect on the tumor but are linked to a statistically significant increase in patient survival.

For that reason, "overall survival" rather than "progression-free survival" should be the gold standard for evaluating the efficacy of cancer vaccines in clinical trials, according to a new editorial in Cancer Biotherapy and Radiopharmaceuticals.

Robert O. Dillman, MD, NeoStem, Inc. differentiates between the two key endpoints typically used to assess therapeutic cancer vaccines in clinical studies. As cancer vaccines are designed to stimulate an immune response to cancer cells and induce long-term memory recognition of a tumor, they may improve overall survival even if they do not appear to slow the progression of disease.

Although measuring overall survival compared to progression-free survival would usually require longer clinical trials, overall survival may be the only relevant efficacy endpoint, the author concludes.

"This is a timely article considering the number of vaccine and antibody immunotherapy trials ongoing or planned," says the journal's Co-Editor-in-Chief Donald J. Buchsbaum, PhD, Department of Radiation Oncology, Division of Radiation Biology, University of Alabama at Birmingham. "The conclusion that overall survival is the best clinical endpoint for efficacy in therapeutic vaccine and antibody immunotherapy trials in patients with metastatic cancer is based on an analysis of four completed trials."

Citation: Dillman Robert O., 'Cancer Vaccines: Can They Improve Survival?' Cancer Biotherapy and Radiopharmaceuticals, March 6, 2015. doi:10.1089/cbr.2014.1805.