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Quantifying the amount of variation in survival explained by prostate-specific antigen
David A Verbel1, Glenn Heller, William K Kelly
1Department of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. verbeld@mskcc.org
Summary
Prostate-specific antigen (PSA) levels show a statistical association with survival in prostate cancer patients, but do not fully predict outcomes. PSA alone is insufficient as a surrogate for survival in clinical trials.
Area of Science:
- Oncology
- Biostatistics
Background:
- Prostate-specific antigen (PSA) changes are statistically associated with survival in prostate cancer.
- However, statistical association alone does not confirm surrogacy for clinical trial endpoints.
- Quantifying the degree of association is crucial for validating surrogate markers.
Purpose of the Study:
- To explore the relationship between PSA and survival in a population-based cohort.
- To generate a measure quantifying the variation in survival explained by PSA.
- To assess the validity of PSA as a surrogate for survival in clinical trials.
Main Methods:
- Utilized serial PSA measurements from 254 patients with androgen-independent prostate cancer.
- Employed a time-dependent Cox model with a nonlinear log relative risk function.
- Quantified the strength of association between time-dependent PSA and survival.
Main Results:
- Observed a statistically significant association between PSA and survival (P < 0.01).
- Time-dependent PSA explained only 17% of the variation in patient survival.
- 247 deaths occurred among 254 patients, with a median survival time of 13.0 months.
Conclusions:
- PSA measurements alone do not account for the full variation in survival outcomes.
- Other unidentified factors significantly influence survival in this patient cohort.
- Using PSA as a sole surrogate for survival in clinical trial design may yield misleading results.