(005) Assessment of the potential risk of seizure among patients with prostate cancer treated with enzalutamide in China: a non-interventional study

Background: Enzalutamide is approved in China for the treatment of patients with non-metastatic or metastatic castration-resistant prostate cancer. Although a safety signal of seizure has been reported for enzalutamide, seizure incidence in enzalutamide-treated patients in China has not been reported. Thus, a non-interventional post-authorization safety study (NI-PASS) of patients treated with enzalutamide in real-world clinical practice in China was conducted.

Objectives: To evaluate the risk of seizure among patients with prostate cancer treated with enzalutamide in China.

Methods: This NI-PASS used an observational cohort design. Data were extracted from electronic medical records of patients aged ≥18 years with prostate cancer treated at three hospitals/medical centers in China who started enzalutamide treatment between 1 March 2020 and 31 May 2022. Data from comparable patients with prostate cancer treated with an alternative antiandrogen therapy were also collected and analyzed to provide perspective on the enzalutamide results. The index date was defined as the date of first treatment with enzalutamide or an alternative antiandrogen. Observation spanned from the index date through the end of follow-up and included on- and off-treatment periods.

Results: A total of 750 patients with histologically confirmed prostate cancer had received enzalutamide (n=385) or alternative antiandrogen drugs (n=365). Most demographic and clinical characteristics were similar between the two groups. Among patients treated with enzalutamide, 38% had risk factors for seizure compared with 36% treated with alternative antiandrogen drugs. Median follow-up for patients treated with enzalutamide or alternative antiandrogens was 85 days (interquartile range, 28–196 days) and 196 days (interquartile range, 82–321 days), respectively. No seizures occurred during the study period in patients treated with enzalutamide (0%, 95% CI, 0–0.95%). One patient treated with an alternative antiandrogen experienced a seizure event (0.27%, 95% CI, 0.01–1.48%); this event occurred during the on-treatment period. Seizure incidence rates per 100 person-years in the enzalutamide group were 0 (95% CI, 0–3.50) and 0 (95% CI, 0–2.74) for the on-treatment and full follow-up periods, respectively. For the alternative antiandrogen group, the respective incidence rates were 0.58 (95% CI, 0–2.14) and 0.44 (95% CI, 0.00–1.61).

Conclusions: Among patients with prostate cancer in China, risk of seizure was low in both enzalutamide and alternative antiandrogen groups, despite the presence of risk factors for seizure in a substantial proportion of patients.