By Robert Preidt, HealthDay Reporter

(HealthDay)

MONDAY, Feb. 23, 2015 (HealthDay News) -- Choosing active surveillance over treatment for prostate cancer may decrease the odds of survival in men with intermediate-risk cancer, a new study says.

The risk of death over 15 years for men with intermediate-risk prostate cancers who chose close monitoring of their disease was nearly four times higher compared to men with low-risk disease, according to the study.

Researchers analyzed data from 945 prostate cancer patients in Canada between 1995 and 2013. All had chosen active surveillance -- also called watchful waiting -- of their disease. Almost 250 of the men had intermediate-risk prostate cancer. About 700 had low-risk cancer.

If cancer got worse during watchful waiting, patients were offered radiation therapy or surgery. Eighty-six men in the intermediate-risk group received treatment, according to the researchers.

Overall survival rates after 10 and 15 years were 68 percent and 50 percent for intermediate-risk patients. That compared to 84 and 69 percent for low-risk patients, the study noted.

Overall, the researchers found that patients with intermediate-risk disease were almost 4 times more likely to die than those with low-risk disease.

The study is scheduled to be presented at an upcoming American Society for Clinical Oncology (ASCO) meeting.

"For low-risk patients with prostate cancer managed with active surveillance, the risk of dying of prostate cancer is low, validating this approach for this group of patients," Dr. D. Andrew Loblaw, a radiation oncologist at Sunnybrook Health Sciences Centre in Toronto, said in an ASCO news release.

But, he added, more research is needed to figure out which intermediate-risk patients can safely be monitored and which patients need treatment sooner.

This is the first study to compare long-term outcomes of low- and intermediate-risk prostate cancer patients on active surveillance, according to Loblaw and his colleagues.

Active surveillance is considered a standard approach for prostate cancer patients with low-risk disease, as well as for some intermediate-risk patients, the researchers said.

More information

The American Cancer Society has more about prostate cancer.