Background: A survival advantage with apalutamide (APA) combined with androgen deprivation therapy for metastatic castration-sensitive prostate cancer (mCSPC) has been demonstrated in the clinical trial, irrespective of race. However, the incidence of APA-induced skin rash in the Japanese subpopulation is higher than that in the global population. In the present study, we investigated the predictive value of APA dose per body weight for the incidence of skin rash.
Methods: A total of 128 patients with mCSPC treated with APA between January 2018 and December 2022 were retrospectively reviewed. A receiver operating characteristic analysis was performed to identify the optimal APA cutoff dose. In addition to comparing the status of APA-induced skin rash, the progression-free survival (PFS) was compared after propensity score matching.
Results: The optimal cutoff dose predicting the occurrence of skin rash was 3.33 mg/kg. Our cutoff value significantly stratified the 2 groups in time to occurrence of APA-induced skin rash and discontinuation of APA due to skin rash (P = .005 and P = .009, respectively). The incidence of a ≥G3 skin rash in patients receiving ≥3.33 mg/kg was significantly higher than in others (6.5% vs. 19.7%, P = .037). There was no significant difference in the PFS between patients administered <3.33 mg/kg and those administered ≥3.33 mg/kg.
Conclusions: Our data suggest that the drug dosage per body weight may predict the incidence and severity of APA-induced skin rash. Further large-scale prospective studies are needed to validate the predictive value of drug dosage per body weight and identify the optimal cutoff value.
Keywords: Adverse events; Androgen receptor signaling inhibitors; Dose modification; Hormonal therapy; Progression-free survival.
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