Progressive multifocal leukoencephalopathy during 4 years of Palbociclib for advanced breast cancer with a history of follicular lymphoma patient.

A 67-year-old woman with a history of follicular lymphoma and recurrent breast cancer with multiple metastasis developed PML during receiving fluvestrant plus palbociclib. Rituximab and bendamustine had finished 6.5 years ago. Discontinuing palbociclib and using mirtazapine, she is alive a year after diagnosis of PML. It is rare for PML to be diagnosed long after the last dose of rituximab and bendamustine. We will discuss the possible involvement of palbociclib in the course of PML.