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Stage shift in PSA-detected prostate cancers - effect modification by Gleason score
Nora Pashayan1, Paul Pharoah, David E Neal
1Department of Public Health and Primary Care, Institute of Public Health, University Forvie Site, Robinson Way, Cambridge, CB2 2SR, UK. np275@medschl.cam.ac.uk
Journal of Medical Screening
|July 1, 2009
Summary
Prostate-specific antigen (PSA) testing detects earlier stage prostate cancer, but this stage shift varies by Gleason score. The benefit is seen in lower Gleason scores, not higher ones, suggesting screening complexities.
Area of Science:
- Oncology
- Urology
- Public Health
Background:
- Prostate-specific antigen (PSA) testing has influenced prostate cancer detection, potentially leading to a stage shift towards earlier diagnoses.
- Understanding how this stage shift varies by tumor aggressiveness, indicated by Gleason score, is crucial for evaluating screening effectiveness.
Purpose of the Study:
- To determine if the stage shift observed in PSA-detected prostate cancers differs based on Gleason score.
- To investigate the interaction between PSA testing, Gleason score, and cancer stage at diagnosis.
Main Methods:
- A cohort of 1514 men with PSA-detected prostate cancer and 2021 with clinically diagnosed prostate cancer (ages 50-69) were analyzed.
- Logistic regression was used to compare the odds of advanced stage (T3+) disease between PSA-detected and clinically diagnosed cancers, controlling for age.
- The likelihood ratio test assessed interaction between detection mode (PSA vs. clinical) and Gleason score.
Main Results:
- PSA-detected cancers were less likely to be advanced stage compared to clinically diagnosed cancers (OR=0.47).
- A significant stage shift to earlier disease (Gleason <7) was observed in PSA-detected cancers (OR=0.52, P<0.001).
- No significant stage shift was found for higher-grade cancers (Gleason ≥7) in the PSA-detected group (OR=0.84, P=0.1), with evidence of interaction (P=0.03).
Conclusions:
- The stage shift associated with PSA testing is not uniform across all Gleason scores, being more pronounced in lower-grade tumors.
- Potential explanations for the observed stage shift include length bias and overdiagnosis.
- Findings highlight the complexity of PSA screening, impacting understanding of prostate cancer progression and screening targets.
