Goal is to prevent recurrence of cancer following surgery to remove prostate
Doctors at the University of Maryland Greenebaum Cancer Center have started a Phase II clinical study of a new prostate cancer vaccine to harness the body’s immune system to prevent recurrence of the disease. There is no cure for recurrent disease, and each year, about 30,000 men in the United States die from prostate cancer that has spread to other parts of the body.
The vaccine will be tested in men diagnosed with prostate cancer who have had their prostate surgically removed, but still have detectable levels of prostate specific antigen (PSA) in their blood. PSA levels indicate the presence of residual cancer cells, and researchers hope the vaccine will trigger an immune response to PSA and destroy the cancer. The vaccine is a modified fragment of the protein PSA and may stimulate the immune system to find and attack circulating prostate cancer cells.
The study was initiated by the University of Maryland Greenebaum Cancer Center and is sponsored by the National Cancer Institute (NCI). “This will be the first time this PSA vaccine is tested in patients,” says Richard B. Alexander, M.D., the study’s principal investigator who is an associate professor of surgery at the University of Maryland School of Medicine and a urologist at the University of Maryland Medical Center.
“Our goal is to develop an effective therapy to prevent recurrence of prostate cancer. Similar protein-based vaccines have shown great promise in treating other kinds of cancer,” adds Dr. Alexander, who is also chief of the urology service at the Baltimore VA Medical Center.
Researchers plan to enroll 32 patients in the clinical trial. To be eligible, patients must have had surgery to remove their prostate, a procedure known as a radical prostatectomy, and rising PSA levels in their blood. They should not have received chemotherapy or hormonal therapy.
Dr. Alexander says that most men do well after prostate removal surgery. About 80 percent no longer have measurable PSA levels, which means their cancer is likely gone. But the remaining 20 percent of men have detectable PSA levels and are at risk of having recurrent disease. “We know that these men are at very high risk of having their cancer spread, usually to their bones. But it takes about eight years, on average, for the disease to spread, which gives us time to intervene,” Dr. Alexander says. “That is what makes vaccination such an attractive treatment option for prostate cancer.”
Nancy A. Dawson, M.D., director of the Genitourinary Oncology Program at the University of Maryland Greenebaum Cancer Center and a professor of medicine at the University of Maryland School of Medicine, says, “We need better options for our patients with detectable PSA levels after they have had surgery, and we hope that this vaccine will prove to be beneficial.”
“Today, some patients are carefully monitored with no active treatment – what we call ‘watchful waiting’ – while others receive drugs to block a male hormone that spurs the growth of tumors. Still other patients benefit from external radiation therapy, but radiation can have difficult side effects,” says Dr. Dawson, a co-investigator on the study. The other co-investigator is Elena Klyushnenkova, Ph.D., a University of Maryland School of Medicine researcher.
Patients who take part in the clinical trial will receive seven injections of the vaccine, PSA: 154-163(155L), over 26 weeks. The vaccine will be combined with another agent to boost the person’s immune response. “This type of vaccination has been very safe for patients with other malignancies. There is much less experience with vaccination in prostate cancer, but we think this is a reasonable approach,” Dr. Alexander says.
Nationally recognized for his research on the prostate and prostate diseases, Dr. Alexander has developed another protein-based vaccine for prostate cancer that he plans to test in a separate clinical trial. The vaccine being used in the current study was developed at the NCI.
Dr. Alexander became interested in vaccines for prostate cancer while he was studying prostatitis, a painful, non-cancerous condition that primarily affects young adult men. He found that some types of prostatitis are the result of an autoimmune disorder in which the body attacks itself. His vaccine studies are an outgrowth of the discovery that the body’s immune system can be triggered to attack prostate cells. He and his colleagues are now trying to learn whether a vaccine containing specific prostate antigens, or proteins, will stimulate a person’s immune system to attack prostate cancer cells anywhere in the body.
Prostate cancer is the most common malignancy in American men, second to skin cancer, according to the American Cancer Society. More than 230,000 men are diagnosed with prostate cancer each year. About 29,900 men will die of the disease, making it the second leading cause of cancer death in men, behind lung cancer. In many cases, prostate cancer is being caught earlier because of annual PSA tests and digital rectal exams, recommended for men over age 50.
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