Active surveillance may not be the best option for patients diagnosed with intermediate-risk prostate cancer, results of a prospective study suggest.
Among 945 men managed with active surveillance, the risk of dying from prostate cancer within 15 years of diagnosis was nearly fourfold higher for those with an initial diagnosis of intermediate-risk disease than for those with low-risk disease.
“What surprised us was that their actually seemed to be a greater risk of dying of prostate cancer for patients diagnosed with intermediate risk disease and placed on surveillance,” said Dr. Andrew Loblaw, a radiation oncologist at Sunnybrook Health Sciences Centre in Toronto.
“When we actually stratify it by patients in the low-risk category, we see that [active surveillance] is a very safe and reasonable approach, and appropriate in our minds for low-risk patients, in line with the guideline recommendations. But despite the selection factors that we use in our clinic for intermediate-risk patients, we’re still seeing, at least in this analysis, greater risk of dying from prostate cancer, and we think that more research is needed to better identify the group of patients that may be watched conservatively,” he said in a media briefing held covering studies to be presented later at the 2015 Genitourinary Cancers Symposium, jointly sponsored by the American Society of Clinical Oncology ( ASCO ), American Society of Clinical Radiology ( ASTRO ), and Society of Urologic Oncology ( SUO ).
Dr. Charles J. Ryan, who moderated the briefing but was not involved in the study said that the findings are provocative.
“There are a number of things that we don’t know from these data. For example, did some of these patients who were on active surveillance go on to receive local therapy later, what were the subsequent therapies they received for metastatic disease, et cetera. But it is an important point to state the fact that some patients with intermediate risk do in fact die of prostate cancer,” said Dr. Ryan, an ASCO Expert with the departments of medicine and urology at the University of California, San Francisco, Helen Diller Family Comprehensive Cancer Center.
Ontario guidelines: ‘Preferred strategy’
Cancer Care Ontario guidelines for the management of low-risk prostate cancer state that “for patients with low-risk (Gleason score ≤ 6) localized prostate cancer, active surveillance is the preferred disease management strategy.”
In the United States, the National Comprehensive Cancer Network ( NCCN ) recommends active surveillance as an alternative to radiation or surgery in the management of men with low-risk prostate cancer and a life expectancy of 10 years or more. Active surveillance is not, however, recommended for men with intermediate-risk disease.
To see whether there were significant differences in outcomes between patients with conservatively managed low- or intermediate-risk disease, the investigators looked at prospectively collected data on 945 men managed with active surveillance at their center from 1995 through 2013. Of this group, 237 had been diagnosed with intermediate-risk disease, defined as a prostate-specific androgen (PSA) level greater than 10, Gleason score of 7, or clinical stage T2b/2c.
Patients were offered intervention if they had a PSA doubling time of less than 3 years, a change in Gleason score, or clinical disease progression.
The authors found that 10-year overall survival (OS) was 67.3% for patients with intermediate risk, compared with 84.2% for those with low-risk disease, and the respective 15-year OS rates were 50.8% vs. 66.7% (hazard ratio, 2.13; P < .0001).
When they looked at cause-specific survival (CSS) rates, they also found significant differences, with a 10-year CSS for intermediate-risk patients of 97.2%, compared with 98.3% for low-risk patients, and 15-year CSS rates of 88.5% vs. 96.7% (HR, 3.74; P = .01).
The investigators concluded that “active surveillance for intermediate-risk prostate cancer has significantly lower overall survival and cause-specific survival, compared with low-risk patients, and therefore extreme caution should be exercised if it were to be implemented in intermediate-risk patients.”
The data are scheduled for presentation in a poster session at the symposium.