CYP19A1 and breast cancer: Moreover, adverse effects in the ribociclib group included nausea, infection (mainly upper respiratory tract infections and urinary tract infections), fatigue, diarrhea, neutropenia, leukopenia, hypertension, elevated alanine aminotransferases, lymphopenia, and QTc interval prolongation.1034 In the clinical trial MONALEESA-7, the efficacy and safety of ribociclib in combination with tamoxifen or nonsteroidal aromatase inhibitors have been observed in the treatment of advanced breast cancer with HR+ and HER2-.