External Validation of the International Staging Collaboration for Cancer of the Prostate (STAR-CAP) Prognostic System in Patients Managed with Active Surveillance.

[UNLABELLED] STAR-CAP is a system for assigning clinical prognostic groups in prostate cancer (PC). The system was developed and validated in patients with PC managed with radical treatment (rTx) with curative intent and outperforms existing systems for risk stratification. We evaluated STAR-CAP in patients managed with active surveillance (AS) in two independent prospective cohorts (Princess Margaret Cancer Centre [PMH] and Sunnybrook Odette Cancer Centre [OCC]) between January 1, 1995, and August 1, 2021. Baseline data were evaluated and patients were categorised into nine STAR-CAP stage groups (IA-IIIC) using a point system for six variables: age, prostate-specific antigen (PSA), cT stage, cN stage, Gleason grade, and percentage positive cores. PC-specific mortality (PCSM) and progression to rTx were quantified across the STAR-CAP groups. Of the 4099 men included, 86% had cT1a-c disease and 89% had grade group 1 PC. PSA at diagnosis ranged from 4.0 to 7.9 ng/ml. Median follow-up was 5.7 yr at PMH and 10.8 yr at OCC. The proportion of patients who went on to receive rTx was 30% at PMH and 43% at OCC. The estimated 10-yr and 15-yr PCSM incidence rates were 0.4% (95% confidence interval [CI] 0.1-1.0%) and 1.1% (95% CI 0.3-2.9%) at PMH, and 1.35% (95% CI 0.79-2.18%) and 3.15% (95% CI 2.14-4.47%) at OCC, respectively. Calibration analysis showed close agreement between observed and STAR-CAP-predicted PCSM. Our external validation supports use of STAR-CAP as a singular classification system and nomenclature for more consistent decision-making across the PC continuum.

[PATIENT SUMMARY] We looked at how well a tool called the STAR-CAP system predicts outcomes for men diagnosed with prostate cancer who are on active surveillance instead of undergoing immediate treatment. After 10 years and 15 years, only a small number of men in the lowest STAR-CAP categories had died from prostate cancer. STAR-CAP can help doctors and patients make better informed decisions on how to manage their prostate cancer.