Vaccine Therapy for Patients with Progressive Stage D0 Prostate Cancer
Name of the Trial
Phase I Randomized Pilot Study of Epitope-Enhanced TARP Peptide Vaccine Versus TARP Peptide-Pulsed Dendritic Cells in Patients with Biochemically Progressing Stage D0 Prostate Cancer (NCI-09-C-0139).See the protocol summary.
Dr. Jay A. Berzofsky, NCI Center for Cancer Research
Why This Trial Is Important
Treating early-stage prostate cancer with surgery or radiation therapy provides long-term disease-free survival for the majority of patients, but between 30 and 40 percent of men will experience a recurrence of their disease within 10 years. When prostate cancer recurs, those who are eligible often receive androgen deprivation therapy, which can be very effective initially. Eventually, however, the cancer acquires the ability to grow without the help of male hormones, and then the outlook is poor.
Scientists believe that immunotherapy has great potential as an alternative approach in treating recurrent prostate cancer, if it can be used as soon as increasing PSA blood levels indicate that the cancer has recurred and has likely spread beyond the prostate. In the Jewett staging system for prostate cancer, this is called stage D0 disease.
In this phase I trial, researchers are testing a vaccine to treat stage D0 prostate cancer. The researchers are evaluating the safety of the vaccine and whether the body’s immune system will respond to it by producing immune cells called T lymphocytes that will selectively attack cancer cells.
Specifically, the vaccine is designed to stimulate the immune system to attack cancer cells that express a protein called T-cell receptor gamma alternate reading frame protein, or TARP, which has been found in more than 90 percent of prostate cancer samples. The vaccine is made by combining natural and modified fragments (peptides) of TARP that were shown in previous laboratory and animal studies to stimulate T-lymphocyte immune responses.
Because the best method of administering the TARP peptides is unclear, the researchers are testing two different approaches. Half of the patients will receive the peptides along with an immune adjuvant, which is a substance that enhances immune responses set in motion by other agents (vaccines, bacteria, viruses, etc.). The remaining patients will be injected with dendritic cells that were taken from their bodies and exposed to the TARP peptides in the laboratory. Dendritic cells are immune cells that take up substances and display them on their surface to T lymphocytes, stimulating an immune response. Using dendritic cells in this way has shown promise in animal and some human studies.
“This setting is an opportunity to take advantage of recent advances in immunotherapy,” said Dr. Berzofsky. “We are starting to harness the exquisite specificity of the immune system to selectively target cancer cells without harming a patient’s normal cells.”