Virus eyed as new treatment for prostate cancer
CTV.ca News Staff
Published Tuesday, March 9, 2010 1:50PM EST
Canadian researchers are working on a fascinating new way to treat prostate cancer using viruses. And while it's still early days, they say their research opens the door to more effective cancer therapies with fewer side effects.
The treatment uses something called oncolytic viruses, which are viruses that seek out cancer cells, invade them and destroy them.
While there are a few naturally-occurring oncolytic viruses, in the last decade scientists have been studying how to genetically engineer them to attack specific cancer tumours.
The idea is that the viruses will attack cancer cells while leaving healthy tissues alone, offering an alternative to current cancer treatments, such as chemotherapy and radiation, which destroy healthy cells as they work.
The new therapy being developed by Alberta researchers uses a reovirus, from a family of common viruses that cause mild, even undetectable, stomach and respiratory illnesses.
The virus they use has already shown potential to attack many types of cancer cells, including lymphoid, ovarian, and breast cancer. To test how well it worked against prostate cancer, researchers led by Dr. Don Morris, a medical oncologist in the Department of Oncology at the Tom Baker Cancer Center in Calgary, recruited six men for a Phase 1 trial.
All the men had early-stage, treatable prostate cancer. Researchers took the reovirus and injected it into a suitable cancer nodule within each man's prostate.
Three weeks later, Morris and colleagues removed the men's prostates as part of the patient's standard treatment. They then analyzed the tissue to see how well the reovirus worked.
"When we first saw these results, the safety and efficacy activity in human patients, ecstatic would be the word," Morris told CTV News. "The success in the first six patients' trial was everything we hoped for and perhaps more."
They found that in that short time, the virus appeared to dstroy a number of the cancer cells, while also sending out copies of itself to attack more cancer cells.
And, to the relief of researchers, the virus stayed confined to cancer cells and didn't spread into normal tissue. What's more, the treatment caused only modest side effects, such as mild flu-like symptoms.
The results are published in Cancer Research, a journal of the American Association for Cancer Research.
The researchers say their hope is that with longer study, the virus therapy will allow doctors to shrink tumours so that they can be more effectively treated by chemotherapy. The therapy might also mean a reduction in the number of men who need prostate removal surgery, which can often bring bad side effects, such as incontinence and impotence.
The Calgary researchers are now hoping for a longer and larger study.
"It strikes me as a very innocent method to study in patients, and I would be very happy to move forward with a bigger trial," says study co-author Dr. Bryan Donnelly, a surgical oncologist at the University of Calgary.
Robert Clarke, a professor of oncology at Lombardi Comprehensive Cancer Center at Georgetown University and an editorial board member of Cancer Research, said he believes this study is worthy of subsequent clinical trials.
"I think this is an interesting approach," said Clarke, who was not associated with this study.
"There is not a lot done in oncolytics, but clearly it is an area that is getting increasing attention, and we need everything we can get our hands on to make a difference in these patients."
Funding for the research was provided by the Alberta Cancer Foundation, the Prostate Cancer Research Foundation of Canada, and Oncolytics Biotech Inc.
Oncolytics Biotech is now studying the reovirus on other forms of cancer, such as those that affect the head and neck, liver cancer, even breast and brain tumours.
With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip