CDK4 and Decreased total neutrophil count: Similarly, Kubeczko et al., in a single-institution experience involving 34 patients treated with SBRT and CDK4/6 inhibitors across 44 metastatic sites (70.4% bone lesions), reported two cases of grade 3 neutropenia and one case of grade 4 neutropenia, for an overall rate of 8.8% [19].