Association between PSA kinetics and cancer-specific mortality in patients with localised prostate cancer: analysis of the placebo arm of the SPCG-6 study
Menée sur 263 patients atteints d'un cancer localisé non traité de la prostate et bénéficiant d'une surveillance médicale, cette étude analyse l'association entre divers indicateurs mesurant l'évolution du niveau du PSA et la mortalité spécifique
Background : The prognostic value of 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 two 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 ng/mL, 10.1-25 ng/mL, and >25 ng/mL. Cumulative incidences of PCa-specific mortality were estimated with the Aalen-Johansen method.
Results : 263 patients were included of which 116, 76 and 71 had a PSA at consent ≤10 ng/mL, 10.1-25 ng/mL, and >25 ng/mL, respectively. Median follow-up was 13.6 years. For patients with PSA at consent between 10.1-25 ng/mL, the 13-year risks of PCa mortality were associated with PSA kinetics: PSAdt ≤3 years: 62.0% vs. PSAdt >3 years: 16.3% (Gray's test: p<0.0001), PSAvel >2 ng/mL/year: 48.0% vs. PSAvel ≤2 ng/mL/year: 11.0% (Gray's test: p=0.0008), and PSAvRC 2: 45.0% vs. 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 ng/mL 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
Annals of Oncology , résumé, 2015