ERBB2 and breast cancer: In the MONARCH 2 trial, which compared abemaciclib plus fulvestrant to placebo plus fulvestrant in women with hormone receptor positive, HER2 negative advanced breast cancer, self-reported that cognitive functioning was significantly improved with abemaciclib plus fulvestrant compared to placebo plus fulvestrant (HR 0.73, 95% CI 0.57–0.92) [58].