Ippolito E, et al. - Researchers studied patients with hormone-receptors positive metastatic breast cancer in order to assess the early toxicity of concurrent use of radiotherapy in association with CDK4/6 inhibitors (palbociclib or ribociclib). With 24 radiotherapy treatments, 16 consecutive metastatic breast cancer patients were analyzed. Palbociclib was received by 13 patients (81.3%), and 3 (18.7%) patients were treated with ribociclib concurrently with RT (18 and 5 radiotherapy courses respectively). Palliative radiotherapy to the bones was received by most of the patients (68.7%). Findings suggested good tolerability of concomitant treatment of CDK4/6 and radiotherapy. A common finding was the presence of high grade hematological toxicity, though it did not alter treatment course in the majority of patients. Because of the usual reoccurrence of previous toxicity, it requires careful assessment.