ERBB2 and breast cancer: In the MONALEESA-2 study, results from the bone-only disease subset (ribociclib group, n = 69; placebo group, n = 78) were similar to those in the overall population (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.