The study conducted by Carter et al. [17], to evaluate the use of abemaciclib in patients with HR+/HER2- advanced breast cancer within the first year of FDA approval, reported a lower incidence of diarrhea of any grade compared with clinical trials (67% vs. ~85%), and a higher number of treatment discontinuation (12% vs. <3%) and hospitalization due to diarrhea (6.8%). This evidence concerns the gene ERBB2 and breast cancer.