Symptomatic bone marrow involvement (bone marrow carcinomatosis) is extremely rare in metastatic breast cancer and carries very poor prognosis. It is often associated with microangiopathic hemolytic anemia and DIC. Anemia is the most common manifestation and WBC and platelet counts are often not tha...

Bone marrow invasion in breast cancer is not uncommon, but it is typically focal in distribution and does not affect the blood counts, unless it becomes diffuse. Once there is diffuse spread, patients develop increasing degrees of anemia and thrombocytopenia, and less often some degree of neutropeni...

Assuming this patient has progressed through AI+CDK4/6, SERD+CDK4/6 and there is no evidence of PI3KCA mutation or BRCA mutation on NGS, I would recommend capecitabine given the ease of administration/monitoring and transfusion support PRN. I would consider EPO, and would recommend IV Iron if the pa...

If the degree of bone marrow involvement is mild to moderate resulting in mild to moderate pancytopenia, I have seen very good results with various CDK4/6 agents. Otherwise, single agent chemotherapy is recommended. I usually start with weekly taxol with reduced dose sometimes. 

Definitely a challenging clinical situation. I agree that cytotoxic chemotherapy should be administered based on the smaller studies mentioned by@Praveen Vikas. Due to ease of oral administration of capecitabine (although with a different side effect profile) and not being myelosuppressive, that wo...