Surveillance Risky in Intermediate-Risk Prostate Cancer?

In an analysis that included 945 patients, intermediate-risk prostate cancer patients managed with active surveillance had worse outcomes compared with low-risk patients managed with surveillance. Over 15 years, the chance of dying from prostate cancer among intermediate-risk patients was 3.75 times higher.

The results were presented by study author Andrew Loblaw, MD, a radiation oncologist at Sunnybrook Health Sciences Centre in Toronto, Canada, at a presscast earlier this week ahead of the annual 2015 ASCO Genitourinary Cancers Symposium, held February 26–28.

Intermediate-risk prostate cancer was defined as a prostate-specific antigen (PSA) level greater than 10 ng/mL, Gleason score 7, or clinical stage T2b/2c.

According to the authors, this is the first study to compare long-term outcomes of patients with intermediate- and low-risk prostate cancer.

The 10-year overall survival rates were 67.3% and 84.2% among intermediate-risk and low-risk patients, respectively. The 15-year overall survival rates were 50.8% and 66.7% among intermediate-risk and low-risk patients, respectively. At 15 years after diagnosis, intermediate-risk patients had an 11.5% risk of dying from their prostate cancer compared with 3.7% for low-risk patients.

Active surveillance is a safe and reasonable strategy that is appropriate for low-risk patients and in line with current recommendations, said Loblaw during the presscast.

“What surprised us was that there seemed to be a greater risk of dying of prostate cancer for patients with the intermediate-risk and placed on surveillance,” said Loblaw.

According to the study authors, there is still a group of intermediate-risk patients that could benefit from active surveillance, but they need to be identified.

“We believe that more research is needed to better identify those patients that may be watched conservatively,” said Loblaw.

The prospective analysis included 237 patients with intermediate-risk disease and 708 patients with low-risk disease, all of whom were on active surveillance at the Sunnybrook Health Sciences Centre in Canada between 1995 and 2013. The median follow-up was 6.4 years, with some patients followed for nearly 20 years. Among intermediate-risk patients, 86% had disease worsening and received either radiation therapy or surgery. Unlike the palliative approach of watchful waiting, the goal of active surveillance is to cure prostate cancer.

Active surveillance is a generally accepted approach for low-risk prostate cancer patients and certain intermediate-risk patients who receive physical exams, digital rectal exams, PSA measurements, and needle tumor biopsies. “For low-risk prostate cancer, it is well recognized that we are probably overtreating these patients, and that is resulting in significant morbidity of the individual patient but also results in costs to the healthcare system,” said Loblaw.

While intermediate-risk patients are increasingly being categorized into favorable and unfavorable groups, the current study did not distinguish patients in this way. Dr. Loblaw stated during the presscast that the analyses are now ongoing to classify the patients into these categories.

This work was funded by Prostate Cancer Canada and internally by the Sunnybrook Health Sciences Centre.