Table 4.

Case reports and clinical studies with CDK4/6 inhibitors in combination with IR

Authors	Patients	Arm	Toxicity	Efficacy
Hans et al. [83]	Metastatic breast cancer (HR+/HER2-) n = 5	Palbociclib + Fulvestrant + palliative IR	Digestive toxicity: mucositis (grade 1 = 20%, grade 2 = 20%) Hematological toxicity: grade 3 neutropenia = 40%, grade 3 anemia = 20%, grade 3 thrombopenia = 40% No skin toxicity	Symptom control and pain relief (100%)
Ippolito et al. [84]	Metastatic breast cancer (HR+) n = 16	Palbociclib or Ribociclib + palliative IR	Hematological toxicity: neutropenia (grade 2 = 12.5%, grade 3 = 25%, grade 4 = 6.3%)	Absent
Figura et al. [85]	Brain metastatic breast cancer (HR+) n = 15 lesions = 42	Palbociclib or Abemaciclib + SBRT	Radionecrosis (2 lesions, 5%) No neurologic toxicity or scalp toxicity	Median OS 36.7 months Six-month local control (88%) Six-month distant brain control (61%)
Chowd-hary et al. [86]	Metastatic breast cancer (HR+/HER2-) n = 16	Palbociclib + Fulvestrant or Letrozole + palliative IR	Hematological toxicity: grade 1 = 87.5%, grade 2 = 12.5% No grade 2 or higher cutaneous, neurologic, or gastrointestinal toxicity	Local control and pain relief (100%)