Publication

Association between PSA kinetics and cancer-specific mortality in patients with localised prostate cancer: Analysis of the placebo arm of the SPCG-6 study.

Thomsen FB, Brasso K, Berg KD, Gerds TA, Johansson JE, Angelsen A, Tammela TL, Iversen P. Scandinavian Prostate Cancer Group.

Ann Oncol. 2016

Abstract

Background
The prognostic value of prostate-specific antigen (PSA) kinetics in untreated prostate cancer (PCa) patients is debatable. We investigated the association between PSA doubling time (PSAdt), PSA velocity (PSAvel) and PSAvel risk count (PSAvRC) and PCa mortality in a cohort of patients with localised PCa managed on watchful waiting.

Patients and methods
Patients with clinically localised PCa managed observationally, who were randomised to and remained on placebo for minimum 18 months in the SPCG-6 study, were included. All patients survived at least 2 years and had a minimum of three PSA determinations available. The prognostic value of PSA kinetics was analysed and patients were stratified according to their PSA at consent: ≤10, 10.1–25, and >25 ng/ml. Cumulative incidences of PCa-specific mortality were estimated with the Aalen-Johansen method.

Results
Two hundred and sixty-three patients were included of which 116, 76 and 71 had a PSA at consent ≤10, 10.1–25, and >25 ng/ml, respectively. Median follow-up was 13.6 years. For patients with PSA at consent between 10.1 and 25 ng/ml, the 13-year risks of PCa mortality were associated with PSA kinetics: PSAdt ≤3 years: 62.0% versus PSAdt >3 years: 16.3% (Gray’s test: P < 0.0001), PSAvel ≥2 ng/ml/year: 48.0% versus PSAvel <2 ng/ml/year: 11.0% (Gray’s test: P = 0.0008), and PSAvRC 2: 45.0% versus 0–1: 3.8% (Gray’s test: P = 0.001). In contrast, none of the PSA kinetics were significantly associated with changes of 13-year risks of PCa mortality in patients with PSA at consent ≤10 or >25 ng/ml.

Conclusion
We found that magnitude changes in 13-year risks of PCa mortality that can be indicated by PSA kinetics depend on PSA level in patients with localised PCa who were managed observationally. Our results question PSA kinetics as surrogate marker for PCa mortality in patients with low and high PSA values.
Clinical trial number
NCT00672282.