Abstract

Cyclin-D-cyclin dependent kinase 4/6 (CDK 4/6) inhibitors started a new era in metastatic hormone receptor positive breast cancer. Ribociclib, palbociclib and abemaciclib (CDK 4/6 inhibitors) are used in combination with endocrine therapy and they provided a significant benefit in progression free and overall survival. Fatigue, neutropenia, anemia, and diarrhea are commonly seen side effects which are easily manageable with dose modifications. Herein, we presented a case of deep vein thrombosis developed twice under palbociclib treatment which is a rarely reported side effect causing cessation of the treatment.