Time-to-event Outcomes in Men with Nonmetastatic Castrate-resistant Prostate Cancer-A Systematic Literature Review and Pooling of Individual Participant Data

Abstract

Context: Until recently, there has been a lack of evidence-based treatment alternatives in men with nonmetastatic castrate-resistant prostate cancer (NM-CRPC). However, new evidence-based treatment alternatives are emerging.

Objective: We aimed to describe time-to-event outcomes in NM-CRPC patients based on evidence from both prospective and retrospective studies. Second, we aimed to describe predictors of these outcomes in the same patient population.

Evidence acquisition: A systematic review was conducted to identify clinical studies (both prospective and retrospective) in NM-CRPC patients. All published Kaplan-Meier curves were digitized, and individual participant data were extracted using a published and validated R code. The following outcomes were considered: overall survival (OS), bone metastasis-free survival (BMFS), time to bone metastasis (TTBM), metastasis-free survival, time to metastasis, time to progression (TTP), progression-free survival, and time to prostate-specific antigen (PSA) progression. Second, we described all predictor/outcome relationships.

Evidence synthesis: Median survival times, in months, for OS, BMFS, TTBM, and TTP in placebo arms of randomized clinical trials are 45.3 (95% confidence interval [CI]: 43.5-46.8), 31.5 (95% CI: 28-33.4), 28.8 (95% CI: 25.2-31.6), and 22.2 (95% CI: 19.3-24.8), respectively. In general, reported outcomes in retrospective studies seemed to be longer than those reported in clinical trials. Baseline PSA nadir levels, PSA doubling time, PSA velocity, and alkaline phosphatase velocity are reliable predictors of time-to-event outcomes in NM-CRPC patients, whereas Gleason score is not.

Conclusions: NM-CRPC is a long-standing condition where effective treatments to slow down disease progression historically have been lacking. Compared with prospective studies, retrospective studies have had limited ability to correctly identify NM-CRPC patients and estimate time to different outcomes in NM-CRPC patients.

Patient summary: For patients with nonmetastatic castration-resistant prostate cancer (NM-CRPC), currently no effective treatments resulting in longer survival compared with watchful waiting are available. On average, without additional treatment, half of these patients survive <45 mo after NM-CRPC diagnosis.

Keywords: Disease burden; Nonmetastatic castration-resistant prostate cancer; Time to event; Treatment.