Skin rash induced by apalutamide correlated with age and relative dose intensity adjusted by body surface area in Japanese patients with prostate cancer.

Abstract

Objective: Common adverse events associated with apalutamide include skin rashes and occur more frequently in Japanese patients. This study used relative dose intensity (RDI) and body surface area (BSA) to investigate the risk of skin adverse events and the efficacy of apalutamide in patients with prostate cancer.

Methods: We retrospectively reviewed data from 63 patients with prostate cancer who were treated with an initial dose of 240 mg apalutamide, and RDI (%) was calculated. Patient backgrounds were compared, and factors contributing to rash development were analyzed. Progression-free survival (PFS), defined as the time to castration-resistant prostate cancer, was analyzed using overall RDI/BSA in metastatic castration-sensitive prostate cancer (mCSPC) patients.

Results: The receiver operating characteristic curve analysis showed that RDI/BSA had a slightly stronger association with rash occurrence than RDI/kg. Univariate analysis identified age and RDI/BSA as significant risk factors for rash occurrence, particularly when both an age cutoff of 72 years and a RDI/BSA cutoff of 56 were met. PFS in mCSPC patients showed no significant differences among tRDI/BSA groups (<36, 36-55, >55) or between patients with and without dose reductions. Cutoff points (36 and 55) were based on the maximum tRDI/BSA values assuming continuous administration of 120 mg or 180 mg apalutamide in patients with a minimum BSA of 1.36 m2.

Conclusions: Age and RDI/BSA were associated with rash occurrence, suggesting a need for dose reduction of apalutamide. A dose reduction to 180 or 120 mg may be appropriate in such cases when considering efficacy.