Background: Prostate cancer screening has led to increased detection of low-grade, localized disease; however, it is unclear whether treatment at this stage is beneficial, especially in older men. Only one randomized study has shown a survival benefit from treatment in this age group, and this benefit was less pronounced than in younger men. Several large, randomized trials are ongoing. The authors conducted an observational study to determine whether radiation treatment or radical prostatectomy resulted in better survival outcomes than observation in men 65 to 80 years of age with early disease.
The Study: Data were taken from a Medicare database incorporating detailed information on tumor characteristics. Men diagnosed with T1 or T2 tumors were considered at low risk and were included in the 12-year study. Those who died within the first study year were excluded from analysis. Survival data in those who received treatment (radical prostatectomy or radiation) and those opting for watchful waiting were gathered, along with extensive information on comorbidities and sociodemographic characteristics. Statistical analyses included calculation of propensity scores and adjustments for multiple factors that could bias the results.
Results: Of the 44,630 patients in the final analysis, 12,608 (28.25 percent) were in the observation group and 32,022 (71.75 percent) were in the treatment group. Because five sociodemographic characteristics were associated with treatment, the authors divided the cohort into quintiles based on propensity scores—a statistical approach designed to balance these predictors.
A total of 12,302 patients (27.6 percent) died by the end of the study: 4,663 (37 percent) in the observation group and 7,639 (23.8 percent) in the treatment group. Adjusting for tumor grade and size resulted in significant improvement in survival with treatment. This was similar when adjustments were made for comorbidities (estimated association between treatment and survival = 0.71; 95% confidence interval, 0.69 to 0.74). The mortality risk reduction was slightly attenuated in the older age groups. These findings remained similar regardless of site, indicating that benefits were not subject to regional variation. In addition, no type of treatment was superior to another.
Conclusion: The authors found that patients undergoing treatment within six months of localized prostate cancer diagnosis were 30 percent less likely to die of prostate cancer over 12 years of follow-up. Although this was an observational study, its strength lies in the quality of statistical analysis, reducing the probability of unknown confounders.
editor's note: In an accompanying editorial, Litwin and Miller note that the absolute numbers of persons benefiting from treatment are small because far more patients will die of other causes earlier than they would have died from prostate cancer.1 Because this observational study did not assess the impact of treatment on quality of life, the authors of the editorial advise continuing the practice of individualized counseling. Results of randomized trials will soon shed additional light on the clinical implications of this study.—c.w.