Anti-Cancer Vaccine May Fight Tumor Growth

Scientists are working to develop therapeutic vaccines that may thwart advanced cancers; however, only a small number of patients have responded to treatment.

A new therapeutic vaccine developed from a genetically modified virus may be an effective treatment for certain advanced cancers, a recent study found. In early clinical trials, the vaccine activated an immune response that blocked tumor growth in a small number of patients.

Preventive vaccines that guard against the cancer-causing human papillomavirus and hepatitis B virus are increasingly viewed as a means to prevent cancer in healthy individuals. Only one vaccine—Dendreon’s Provenge, used to treat prostate cancer—has been approved by the FDA for the treatment of patients who already have the disease, however.

Lead author Michael Morse, MD, said therapeutic vaccines work by activating the immune system to "attack tumors by causing them to recognize antigens, proteins that appear foreign to the immune system." Those immune cells can be defective in patients with cancer, making it more difficult for them to fight tumor growth, according to Dr. Morse.

A gastrointestinal oncologist at Duke University School of Medicine, Dr. Morse has focused his research on vaccines that target dendritic cells, which are the body’s main immune stimulators. “So far, we’ve been seeing signs that we are activating the immune system to recognize cancers, and our goal is to get better and better at stimulating the immune system,” he wrote in a profile for the Duke Comprehensive Cancer Center.

To create the latest vaccine, Dr. Morse and colleagues used an equine encephalitis virus modified with carcinoembryonic antigen (CEA), which is a common biomarker expressed in colon, breast, lung, and other cancers. The researchers then administered the treatment to 28 patients with advanced colorectal, appendix, pancreas, lung, and breast cancer who had failed 4 previous rounds of chemotherapy.

A total of 5 patients responded to the treatment. Two patients reached a stable condition; 2 who had been in remission stayed in remission; and 1 who had a small liver lesion showed “complete response,” with the lesion disappearing following the vaccination.

Although the results were promising, according to the authors, “the numbers were small and there were not enough events to make a statistical comparison.” The study was published online August 2, 2010, in the Journal of Clinical Investigation.

Resources for Pharmacists

Research to investigate the tumor-fighting potential of therapeutic vaccines is still in its early stages. For a current list of clinical trials of treatment vaccines by cancer type, visit the National Cancer Institute’s Cancer Vaccine Fact Sheet.

For most patients already struggling with advanced cancer, vaccines are not yet an option. Under these circumstances, compassionate counseling can help preserve balance between the gravity of a terminal diagnosis and the optimism needed to survive on a day-to-day basis.

For more information on counseling patients with cancer and other terminal illnesses, read “Coping with Terminal Illness,”

written by Guido R. Zanni, PhD, and Charles L. Browne III, JD, and published in the August Oncology issue of Pharmacy Times.

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