Prognostic factors of prostate cancer mortality in a Finnish randomized screening trial

Objectives: To identify the prognostic factors of prostate cancer death among patients enrolled in a Finnish prostate cancer screening trial. Methods: Data on TNM stage, Gleason score, serum prostate-specific antigen at diagnosis, comorbidity and primary treatment were collected from medical records, as well as date and cause of death from Statistics Finland. Four prognostic risk groups were defined based on TNM stage, Gleason score and prostate-specific antigen at diagnosis. Hazard ratios and their 95% confidence intervals for prostate cancer death were calculated using Cox regression and competing-risk analysis with follow up from randomization. The differences in the effects of prognostic factors were assessed using interaction terms. Results: The 15-year survival was significantly lower among cases in the control arm compared with the screening arm (0.90 vs 0.92). However, the survival advantage was limited to screen-detected cases (0.94 vs 0.91 in cases detected outside screening). The prognostic risk group was the strongest factor predicting survival in the control arm, but weaker in screen-detected cases. Advanced disease was associated with substantially poorer outcome in cases detected outside screening than in screen-detected disease. Primary treatment had a similar effect in all groups. Comorbidity had a small prognostic effect in the control arm only. Conclusions: Prognostic factors had a different effect on the outcome of cases detected through screening as those diagnosed otherwise. A high diagnostic prostate-specific antigen and advanced disease carried a poor prognosis, especially among the cases detected outside screening, even when lead-time was eliminated. This shows that the screening resulted in earlier treatment among the cases in the screening arm.

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