The study, published in this month's edition of Cancer Research, shows that patients experienced no significant side effects when treated with gene therapy and radiation therapy. It also showed that the treatment lowered patients' prostate-specific antigen (PSA) and eliminated the cancer in many of them.
PSA is a protein produced by the prostate. By measuring its level, doctors can monitor prostate cancer growth as well as the effectiveness of standard and investigational treatments.
All 15 patients enrolled in the study experienced significant declines in their PSA - from an average of 12 to below one - and 10 of them were cancer-free after one year. The patients had an aggressive form of prostate cancer that, if treated with standard radiation therapy alone, would likely recur and possibly spread.
While the results are encouraging, researchers say more research is needed and the novel treatment needs to be tested in a larger randomized clinical trial, which is planned for next year.
"Our belief is that gene therapy could make conventional cancer therapies such as radiation therapy more effective," says Svend Freytag, Ph.D., division head of Henry Ford's Radiation Oncology Research and lead author of the study.
The study is the first of its kind in the world to test the safety and effectiveness of a replication-competent virus in combination with radiation therapy. The replication-competent virus used in the treatment - the one associated with the common cold - has been shown to enhance the gene therapy's effectiveness by spreading the gene therapy to nearby cells after it is injected into the prostate.
The virus kills the cancerous cells, but leaves normal ones undamaged. When combined with the gene therapy, it enhances the virus' effect by rendering the malignant cells sensitive to radiation therapy.
An estimated 220,900 new cases of prostate cancer will be diagnosed this year, and nearly 29,000 men will die of it, according to the American Cancer Society. Prostate cancer is the second-leading cause of cancer death in men, after lung cancer.