Recently, a long-term clinical trial shows that combining radiation treatment with "suicide gene therapy" provides a safe and effective one-two punch against prostate cancer. Suicide gene http://www.cusabio.com/ therapy is a technique in which prostate tumor cells are genetically modified so they signal a patient's immune system to attack them. Prostate cancer is the most common cancer in men and causes significant mortality. The study is conducted by tumor researchers at Houston Methodist Hospital.
The researchers compared two arms of patients and report high five-year overall survival rates of 97 percent and 94 percent, respectively. That's a 5 to 20 percent improvement for survival over historical studies.
Sixty-six prostate tumor patients participated in the Phase II clinical trial between 1999 and 2003 and were split into two groups. One group with cancer cells confined to the prostate, designated Arm A, received only radiotherapy. The other with a more aggressive prostate cancer, designated Arm B, received both radiation and hormonal therapies. Patients in Arm A received the experimental gene therapy twice during the study, while the Arm B group received the treatment three times.
The researchers used an adenovirus, which is similar to the one that causes the common cold, to carry the therapy agent directly into the tumor cells. The therapy agent is a herpes virus gene that produces the enzyme thymidine kinase, or TK. Once the herpes virus gene was delivered and it started manufacturing TK, the researchers gave patients a commonly used anti-herpes drug, valacyclovir. The combination attacked the herpes DNA, and the TK-producing tumor cells self-destructed, which is why the procedure is called suicide gene therapy.
The immune system of patients is previously unaware of the cancer's presence. Once the activated valacyclovir starts destroying tumor cells, it also stimulates the patient's immune system to attack the prostate tumor cells.
The researchers have created a vaccine with the patient's own cancer cells, a treatment that complements and even enhances the achievement that traditional radiation and hormonal therapies make.
According to the study, the long-term outcome for prostate cancer patients receiving gene therapy in combination with radiotherapy with or without hormonal therapy is promising. The 62 patients in both arms who completed the clinical trial had remarkably high five-year freedom from failure rates, meaning no indication by biochemical testing of cancer recurrence, of 94 percent and 91 percent, respectively. Prostate biopsies performed at 24 months after completion of treatment were negative in 83 percent of Arm A patients and 79 percent of Arm B patients.
The outcomes were remarkably higher than those achieved with radiotherapy alone for all evaluative factors. The findings may give promise to a novel viable treatment strategy. Furthermore, the majority of patients in the clinical trial experienced little or no side effects or complications. A Phase III patient trial to test the final safety and efficacy evaluation for the in-situ immunomodulatory gene http://www.cusabio.com/catalog-25-1.html therapy is already underway.
