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Real-World Analysis of Apalutamide-Associated Skin Adverse Events in Japanese Patients with Advanced Prostate Cancer: A Multi-Institutional Study in the Chu-Shikoku Japan Urological Consortium - Beyond the Abstract

Skin rash is one of the adverse events (AE) during the treatment of apalutamide. According to an integrated analysis of phase III and phase I studies, this skin AE is more common in the Japanese population (51.5%) than in the global population (SPARTAN study: 23.8%, TITAN study: 27.1%).1-3 The underlying mechanism of skin AEs and the reason for the high incidence of skin AEs in the Japanese population are poorly understood. Limited clinical information has only hampered further understanding. Therefore, we aimed to investigate the incidence of skin AEs and the association between patient characteristics and skin AEs using data on real world data set, which were collected from multiple institutions in Japan.

In this study, skin AEs were observed in 46.2% of patients, with a median time-to-first incidence of skin AEs of 62 days, and grade 3 skin AEs was observed in 12.6% of the patients. The incidence of skin AEs was also higher than that in the global population in phase 3 clinical trials, such as SPARTAN and TITAN.1,2 Our results were comparable to the integrated analysis of the Japanese cohort in SPARTAN and TITAN: all grades in 51.5% and grade 3 in 14.7%, with a median time to the first incidence of 66 days.3 Therefore, in real-world clinical practice, our data confirmed data from phase 3 clinical trials.

In this study, no significant clinical risk factors, including body weight and BMI, for the incidence of skin AEs were observed, which is also consistent with the integrated analysis of the Japanese cohort in SPARTAN and TITAN.3

In addition, we found that the duration from the onset of skin AEs to apalutamide discontinuation was longer in patients with severe skin AEs than in those with mild skin AEs. This is attributable to the half-life of apalutamide being 110 – 231 h,4 which means that it does not disappear from the plasma immediately after its interruption. Moreover, in clinical practice, we speculated that patients might not pause the consumption of apalutamide until the next clinical visit, even if a skin AE occurs. Therefore, the possibility of worsening skin AEs after apalutamide interruption should be considered in clinical practice.

Written by: Yoichiro Tohi, MD, Department of Urology, Kagawa University, Takamatsu, Japan

References:

  1. Smith MR, Saad F, Chowdhury S, et al (2021) Apalutamide and overall survival in prostate cancer. Eur Urol 79:150–158
  2. Chi KN, Agarwal N, Bjartell A, et al (2019) Apalutamide for metastatic, castration-sensitive prostate cancer. N Engl J Med 381:13–24
  3. Uemura H, Koroki Y, Iwaki Y, et al (2020) Skin rash following Administration of Apalutamide in Japanese patients with Advanced Prostate Cancer: An integrated analysis of the phase 3 Spartan and Titan studies and a phase 1 open-label study. BMC Urol 20:139
  4. Tsuchiya T, Imanaka K, Iwaki Y, et al (2019) An open-label, phase 1 study of androgen receptor antagonist, apalutamide in Japanese patients with metastatic castration-resistant prostate cancer. Int J Clin Oncol 24:1596–1604

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