ERBB2 and breast cancer: Ribociclib + letrozole treatment in patients with visceral metastases exhibited a similar safety profile to that observed in the full population, irrespective of disease burden (Burris HA et al. First-line ribociclib + letrozole in patients with HR+/HER2– advanced breast cancer presenting with visceral metastases or bone-only disease: a subgroup analysis of the MONALEESA-2 trial.