Compared with immediate radical prostatectomy, active surveillance for men with low-risk prostate cancer produces only a "very modest" 1.8-month decrease in cancer-specific survival, according to a report published online Sept. 24 in Clinical Cancer Research.
However, men on active surveillance enjoyed 6 more years of life free from treatment and its adverse effects than men who had immediate surgery, said Dr. Ruth Etzioni of the division of public health services, Fred Hutchinson Cancer Research Center, Seattle, and her associates.
Dr. Ruth Etzioni
These are the findings of a new simulation model they developed to predict prostate cancer mortality in a virtual population of 1 million contemporary U.S. cases, using the best available data from contemporary studies of the issue.
The investigators first incorporated into their simulation model the findings from an active surveillance program in which men with low-risk prostate cancer are biopsied every year and referred for further treatment if any adverse changes are found. This program also allows patients to self-refer for further treatment for several other reasons, including if their prostate-specific antigen level rises or if they become too anxious over "watchful waiting."
The researchers then incorporated into the model information from a large longitudinal database on the interval between radical prostatectomy and recurrence. The Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) database enrolled nearly 14,000 men treated at 40 urology practices, and included 1,000 clinical and patient variables.
Lastly, Dr. Etzioni and her colleagues used data from another cohort study of 3,470 men to model the time from prostate cancer recurrence until death. They then computed the cumulative cancer-specific mortality in their virtual cohort for men under active surveillance compared with men who underwent immediate radical prostatectomy.
The model projected that the 20-year cumulative rate of prostate cancer–specific mortality would be 2.78% with active surveillance and 1.64% with immediate radical prostatectomy. This corresponded with an average of 1.8 months of life saved per case, which was considered a "very modest" advantage, the investigators said (Clin. Cancer Res. 2012 Sept. 24 [doi:10.1158/1078-0432.CCR-12-1502]).
However, the model also showed that men on active surveillance "had on average 6.4 more years of life free from treatment and its side effects," which could be a substantial advantage.
Three separate sensitivity analyses demonstrated that the model’s projections were robust even when multiple variables were altered. "All sensitivity analyses produced only modest differences in cumulative prostate cancer mortality under active surveillance, and supported our projection that active surveillance would have a minimal impact on life expectancy for low-risk cancer cases," Dr. Etzioni and her associates said.
"Ultimately, the model predicts that approximately 64% of men on active surveillance would be treated [for prostate cancer] within their lifetimes. ... Thus, under active surveillance, 36% of men could avoid being treated," they said.
These findings are consistent with those of at least one other modeling study and with those of the longitudinal PIVOT (Prostate Cancer Intervention versus Observation Trial) study that tracked disease-free survival for 12 years.
"Although this is not a new result, it is confirmation of what we expected, and it substantiates data from previous studies looking at watchful waiting. Very few men with low-risk disease die from prostate cancer regardless, and the difference between treatments appears to be very modest," Dr. Etzioni said in a press statement accompanying this report.
This study was supported by the National Cancer Institute and the Centers for Disease Control and Prevention. No financial conflicts of interest were reported.