June 8, 2000. Vaccination against disease is not a new concept, but in the arena of cancer therapies it is viewed as a possible way to kill malignant cells without damaging healthy cells. In this case, the therapy holds promise because it provides an avenue for treating the malignant cells before they become symptomatic.
Participants in the trial are men who have already undergone surgery or radiation therapy for prostate cancer. Subsequent blood tests for prostate specific antigen indicated their cancer has spread. PSA is produced by the prostate, but patients enrolling in this trial have had their prostates removed or treated with radiation so their PSA levels should be very low or undetectable. Participants in the trial must have no symptoms or findings of disease recurrence other than the elevated PSA.
"Because of the PSA blood test, recurrence of prostate cancer can be detected at an earlier stage than it could be previously," said Christopher Sweeney, M.D., an oncologist at the IU School of Medicine and one of the physicians treating trial participants. "It is hoped the vaccine will boost the patient's immune system and eliminate the cancer while it is still at a low level in the body."
Two vaccines are being tested to determine which treatment regimen is most effective. One uses the vaccinia virus, a relatively harmless virus used in smallpox vaccines, and the second uses the fowlpox vaccine. Both are genetically altered viruses that have been changed to express human PSA. The PSA-bearing virus is attacked by the human immune system and, ideally, the body simultaneously will attack the PSA tumor cells.
Patients are treated with four injections six weeks apart and then followed for at least six months to determine if the PSA tumor cells were eradicated. The IU Cancer Center is one of five sites nationwide enrolling patients for the Phase II trial. The trial is sponsored by the Eastern Cooperative Oncology Group, a national cancer clinical trial cooperative group funded by the National Cancer Institute.
Follow Up
This NCI and Eastern Cooperative Oncology Group study, titled PSA Vaccine Therapy in Treating Patients With Advanced Prostate Cancer, was a phase II randomized clinical trial begun in in 1999 and now completed. The link above will take you to NCI's document for patients considering enrollment.
Results appeared in Journal of Clinical Oncology , Vol 22, No 11 (June 1), 2004: online in freely accessible full-text
Phase II Randomized Study of Vaccine Treatment of Advanced Prostate Cancer (E7897): A Trial of the Eastern Cooperative Oncology Group
The trial enrolled 64 eligible patients, who were randomly assigned to receive four vaccinations with fowlpox-PSA (rF-PSA), three rF-PSA vaccines followed by one vaccinia-PSA (rV-PSA) vaccine, or one rV-PSA vaccine followed by three rF-PSA vaccines. The major end point was PSA response at 6 months, and immune monitoring included measurements of anti-PSA and anti-vaccinia antibody titers and PSA-specific T-cell responses.
RESULTS: "The prime/boost schedule was well tolerated with few adverse events. Of the eligible patients, 45.3% of men remained free of PSA progression at 19.1 months and 78.1% demonstrated clinical progression-free survival. There was a trend favoring the treatment group that received a priming dose of rV-PSA. Although no significant increases in anti-PSA antibody titers were detected, 46% of patients demonstrated an increase in PSA-reactive T-cells."
CONCLUSION: Therapy with poxviruses expressing PSA and delivered in a prime/boost regimen was feasible and associated with minimal toxicity in the cooperative group setting.
A significant proportion of men remained free of PSA and clinical progression after 19 months follow-up, and nearly half demonstrated an increase in PSA-specific T-cell responses. Phase III studies are needed to define the role of vaccination in men with prostate cancer or those who are at risk for the disease.
Pomegranate Juice Slows PSA Rise in men With Recurrent Prostate Cancer After Surgery, Radiation
