Apalutamide Treatment Predictor of Metastasis-Free Survival in nmCRPC Patients

Chicago—Patients with nonmetastatic castration-resistant prostate cancer (nmCRPC) and prostate-specific antigen (PSA) doubling time of ≤10 months are at high risk for metastatic disease and associated mortality. In the SPARTAN trial, metastasis-free survival was extended by a median >2 years in men with nmCRPC treated with apalutamide (hazard ratio, 0.28; 95% confidence interval, 0.23-0.35; P<.001). Apalutamide is a next-generation, androgen receptor inhibitor.

Eric Jay Small, MD, and colleagues recently conducted a multivariate analysis of data from SPARTAN to identify independent predictors of metastasis-free survival in that patient population. Results of the analysis were reported during a poster session at the ASCO 2018 Annual Meeting in a poster titled Predicting Disease Progression in Patients (pts) with Nonmetastatic Castration-Resistant Prostate Cancer (nmCRPC): An analysis from the Phase 3 SPARTAN Trial.

The researchers utilized a nonstratified proportional hazards model to assess predictors of clinical end points and to examine covariates including treatment, PSA doubling time, use of bone-sparing agents, N0 versus N1 at study entry, Eastern Cooperative Oncology Group performance status, prior therapies, Gleason score, age, and baseline PSA.

A total of 1207 patients were randomized to receive either apalutamide (n=806) or placebo (n=401). The evaluation included the overall population. Independent predictors of longer metastasis-free survival for the combined arms were: apalutamide treatment, PSA doubling time >6 months, NO disease, Gleason score at diagnosis ≤7, and baseline PSA  ≤8.8 ng/mL. There was a relationship between shorter PSA doubling time and faster time to metastasis or death.

In summary, the researchers said, “Apalutamide treatment, PSA doubling time, nodal disease, Gleason score, and baseline PSA were independent predictors of metastasis-free survival in patients with nmCRPC from SPARTAN. The treatment effect of apalutamide remained highly significant after adjusting for covariates, with a similar magnitude of risk reduction for metastasis-free survival in the multivariate analysis to that of the original primary analysis. Furthermore, there is a continuous relationship between PSA doubling time and time to metastasis or death.”

Clinical trial information: NCT01946204

Source: Small EJ, Saad F, Rathkopf DE, et al. Predicting disease progression in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC): An analysis from the phase 3 SPARTAN trial. Abstract of a poster presented at the American Society of Clinical Oncology 2018 Annual Meeting, June 2, 2018, Chicago, Illinois.