Response and Tolerability of Palbociclib Plus Fulvestrant in Breast Cancer Patient with Bone Marrow Metastasis and Cytopenia: A Case Report

Background: Palbociclib is a potent cyclin-dependent kinase (CDK) 4/6 inhibitor that impairs cell cycle progression. It has recently been approved for patients with hormone receptor positive metastatic breast cancer. Case Report: We report the response achieved palbociclib plus fulvestrant therapy in a 68-year-old female breast cancer patient with bone marrow metastasis. She treated with paclitaxel weekly chemotherapy, but no response was obtained. Then, with dose reduction palbociclib 75 mg/day, plus fulvestrant treatment was administered. After 6 cycles, thrombocytopenia resolved and the palbociclib dose was increased to 125 mg/day. Cytopenia completely resolved after the eight cycle treatments. She is still going on treatment without progression and side effects. Conclusion: The efficacy and safety of CDK 4/6 inhibitors in patients with bone marrow metastases have not been clarified. However, palbociclib treatment can be given with close follow-up and dose reduction in breast cancer patients with bone marrow metastasis.