To the Editor In their randomized clinical trial reported recently in JAMA Oncology, Zong and colleagues examined the efficacy of gonadotropin-releasing hormone analog (GnRHa) treatment administered during chemotherapy for reducing premature ovarian insufficiency among women with breast cancer. Key secondary analyses included overall survival (OS) and tumor-free survival (TFS) among patients younger than 35 years. In particular, 4-year OS and TFS were significantly improved with GnRHa treatment (OS, 100% vs 81%; P = .01; TFS, 93% vs 62%; P = .004). However, this cross-sectional analysis does not take the time to event into consideration. Results from hazard ratio (HR) analysis, which does consider the time to event, were also reported. These supported a difference in the case of TFS (HR, 0.15; P = .03), but not in that of OS (HR, 0.02; P = .37).
