Late onset of apalutamide-related skin toxicity in Black men with advanced prostate cancer: A diverse real-world analysis.

23 Background: Apalutamide (APA)- related skin toxicity is a common adverse reaction of varying incidence by ethnicity 1 . We have limited data on APA-related skin toxicity in Black men due to under-representation in clinical trials 2 . This real-world analysis evaluates APA-related skin toxicity and its differential impact across Black and White men in an ethnically diverse population at two high-volume cancer centers in London, United Kingdom. Methods: We investigated 120 prostate cancer patients treated with APA between 2021 and 2023. Skin toxicity incidence and grading, time to onset and drug discontinuation rates were examined. Adverse event causality was attributed by treating physicians and graded by the Common Terminology Criteria for Adverse Events v5.0 based on body surface area involvement. The cumulative incidence of APA-related skin toxicity and APA discontinuation rates were estimated by Gray’s method. Results: 111 patients were included in our analysis, represented by 35 (31.5%) Black and 76 White men (68.4%). 18 men (16.2%) had pre-existing autoimmune or skin disease. 108 men (97%) commenced APA at 240 mg. At 24-month follow up, APA-related skin toxicity of any grade and Grade 3, were seen in 23 (23%) and 12 men (12%) respectively. There was no significant difference in skin toxicity incidence or severity between Black and White men (Table). The median time to skin toxicity was 179 and 84 days in Black and White men respectively, with late onset (>6 months) events more commonly seen in Black men. APA discontinuation rate due to skin or other Grade 3 toxicity was similar (24-month, 11.4% in Black vs 9.2% in White men). Based on multivariable competing risk analysis, skin or autoimmune disease, or eosinophil count at baseline had no significant impact on incidence or severity of skin toxicity. Conclusions: Late onset of APA-related skin toxicity is seen more commonly in Black men, thus requires clinical vigilance and monitoring. There is no significant ethnicity disparity in incidence or severity for APA-related skin toxicity. No significant risk factors for incidence and severe skin toxicity were identified. Cumulative incidence of APA-related skin toxicity at 6 and 24 months. Skin Toxicity Ethnicity 6-months 24-months p-value Any grade 0.851 White 14% 21% Black 11% 25% Grade 3 0.954 White 9.2% 11% Black 2.9% 13%