TORONTO (CP) - Doctors can prolong the lives of men with advanced prostate cancer for several months and improve their quality of life with a new-generation drug treatment, a Canadian-led international study has found.

The drug, docetaxel, increased survival by an average of three months, and in some cases for six months or longer, compared to standard chemotherapy, said Dr. Ian Tannock, an oncologist at Toronto's Princess Margaret Hospital and lead investigator of the 24-country study.

"This is a small but significant advance in the treatment of prostate cancer," said Tannock. "For the first time, there is a drug that can have a small but definite effect to improve survival in patients" with advanced prostate cancer that has spread to the bone and other parts of the body and become resistant to hormonal treatment.

Prostate cancer can initially be treated by surgical removal of the walnut-sized gland, radiation and/or medications that decrease the production of male hormones like testosterone, which can fuel the growth of cancer cells. But the hormone-reducing therapy may stop working, allowing the cancer to spread.

"The problem is that unless they succumb to some other diseases - and of course this is a disease of elderly people, in general - men with prostate cancer reach a stage where their cancer cells are no longer responsive to hormonal treatment," said Tannock.

The study, published Thursday in the New England Journal of Medicine, involved more than 1,000 men with end-stage prostate cancer in Canada, the United States, Britain, Australia and other countries. Those treated with docetaxel and the steroid prednisone lived an average of three months longer than those in the group taking the standard drug, mitoxantrone, and prednisone.

But beyond living longer, docetaxel also improved the men's quality of life, reducing pain, fatigue and other symptoms, as well as decreasing the amount of PSA - a protein that indicates cancer activity - in their blood.

While an extra three or more months of life may seem short, Tannock said for men facing inevitable death from prostate cancer, any time is a much-desired bonus.

"Life is very precious and everybody is an individual . . . and even a three-month prolongation of life - if it's of reasonable quality - is still quite important."

Still, docetaxel has several "annoying" side-effects, including numbness and tingling in the fingers and toes, watery eyes and nail roughening, Tannock said. Five men on the drug died, although it's not yet known what role it played.

And the medication, which is administered intravenously at out-patient clinics, is also three times the price of mitoxantrone, running at about $2,000 per injection. Patients in the study were given about 10 injections over 30 weeks.

Dr. Andrew Loblaw, a radiation oncologist at Sunnybrook and Women's Health Sciences Centre in Toronto, said the study's findings will lead to a change in how doctors treat the disease. "This opens up a whole new era in the treatment of prostate cancer, especially for men with advanced or end-stage prostate cancer."

"This is the first randomized study to show that any chemotherapy agent actually improves survival in men with prostate cancer. And not only are they living longer, but their life is actually better during that time as well."

Loblaw said the discovery will spur researchers to look at combining docetaxel with other agents and to try the drug at an earlier stage of the disease, "where it may have a bigger impact."

The study was partly funded by Aventis, the company that manufactures docetaxel.

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