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Comment & Response
May 28, 2020

Analysis of Overall Survival Benefit of Abemaciclib Plus Fulvestrant in Hormone Receptor–Positive, ERBB2-Negative Breast Cancer

Author Affiliations
  • 1Department of Biostatistics, University of Texas MD Anderson Cancer Center, Houston
  • 2Hinda and Arthur Marcus Institute for Aging Research, Hebrew SeniorLife, Harvard Medical School, Boston, Massachusetts
  • 3Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
JAMA Oncol. 2020;6(7):1121-1122. doi:10.1001/jamaoncol.2020.1513

To the Editor Sledge and colleagues1 conducted a global, randomized clinical trial of abemaciclib plus fulvestrant vs placebo plus fulvestrant for treating hormone receptor–positive, ERBB2-negative advanced breast cancer. The trial enrolled 669 women, and 446 and 223 patients were assigned to the abemaciclib and placebo arms, respectively. At the interim analysis, 338 deaths were observed. The median overall survival (OS) times were 46.7 and 37.3 months for the abemaciclib and placebo arms. The hazard ratio (abemaciclib vs placebo) was 0.757 (95% CI, 0.606-0.945; P = .01). However, in Figure 2,1 the 2 Kaplan-Meier curves for OS clearly overlapped until month 27, and so the proportional hazards assumption is obviously not valid. Therefore, the estimated hazard ratio of 0.757 is difficult, if not impossible, to interpret clinically.2

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