Real-world clinical usage and efficacy of apalutamide in men with nonmetastatic castration-resistant prostate cancer: a multi-institutional study in the CsJUC.

[OBJECTIVE] To evaluate the real-world clinical usage and effectiveness of apalutamide in men with nonmetastatic castration-resistant prostate cancer (nmCRPC).

[METHODS] We retrospectively reviewed the data of 186 men who received apalutamide across 17 institutions. The primary outcomes were the clinical usage of apalutamide for nmCRPC: prior usage of other androgen receptor signaling inhibitors (ARSIs), prior radical treatment, and the distribution of the prostate-specific antigen (PSA) doubling time (PSA-DT) at the initial administration of apalutamide. The secondary outcomes were the efficacy of apalutamide: PSA response (50% or 90% decline), progression-free survival, and skin-adverse events (AEs).

[RESULTS] We identified 75 patients with nmCRPC. A total of 31 (41.3%) patients received prior treatment with other ARSIs. A total of 42 men (56%) did not receive any prior radical treatment. The PSA-DT was <3.0, 3.0-5.9, 6.0-10, and > 10 months in 34.7%, 40%, 14.7%, and 10.6% of the patients, respectively. Patients receiving prior treatment with other ARSIs showed a significantly lower PSA response (PSA 50% decline, 88.4% vs. 18.8%; PSA 90% decline, 60.5% vs. 6.2%, P < .001, respectively) and significantly shorter progression-free survival (median: 37 months vs. 4 months; log-rank P < .001) than those without prior ARSI treatment, although cancer status did not differ between the groups. Skin-AEs were observed in 42.7%.

[CONCLUSIONS] This real-world study revealed that apalutamide was used for the treatment after other ARSIs in >40% of patients with nmCRPC and showed limited efficacy in this context, although the effectiveness of apalutamide without prior other ARSI treatment was comparable with that reported in clinical trial results.