Men who undergo radical prostatectomy (RP) for a tumor that was detected by screening show better long-term outcomes than their peers who undergo the surgery after opportunistic diagnosis, study results show.
The improved outcomes in the screening group appeared to be largely as a result of them having a significantly lower tumor volume.
"The present results suggest that one of the ways that screening improves survival outcomes is through a reduction in the volume and therefore burden of disease at diagnosis," Stacy Loeb (University Medical Center, Rotterdam, the Netherlands) and colleagues comment.
The researchers examined data from the Rotterdam section of the European Randomized Study of Screening for Prostate Cancer (ERSPC), where 42,376 men were randomized to annual screening for 6 years or treatment as usual that included opportunistic screening.
In all, 1151 men in the screening arm and 210 in the control arm were diagnosed with prostate cancer, respectively.
Of these men, 420 (36.5%) screen-detected cases and 54 (25.7%) controls underwent RP with long-term median follow-up data of 9.9 years.
In terms of characteristics at the start of the follow-up period, RP cases from the screening and control arms had statistically similar clinical stage and biopsy Gleason score, although screen-detected cases had significantly lower prostate-specific antigen (PSA) levels at diagnosis.
Loeb et al report that after RP, men from the screening arm showed better outcomes than their peers in the control arm, with a significantly higher 10-year progression-free survival (88 versus 72%), metastasis-free survival (98 vs 86%), and cancer-specific survival (98 vs 88%).
In multivariable models adjusting for age, PSA level, clinical stage, and biopsy Gleason score, the screening group had a significantly lower risk for biochemical recurrence and metastasis compared with the control arm (hazard ratio [HR]=0.43 and 0.18, respectively).
However, after additionally adjusting for tumor volume and other RP pathology features, there was no longer a significant difference in biochemical recurrence between the screening and control arms.
Leob and colleagues note that in previous studies the lack of a mortality difference between individuals screened for prostate cancer and controls has generated questions about the comparative efficacy of organised and contemporary opportunistic screening.
Nevertheless, the results of the present study "suggest that a reduction in tumor burden at diagnosis is a mechanism through which PSA screening improves treatment outcomes," they comment.
The results are published in the British Journal of Urology International.
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