Definition
Thrombocytopenia is a reduction in the normal levels of functional platelets. It is associated with bortezomib treatment, particularly in patients who have had prior therapies.r
Pathophysiology
Thrombocytopenia associated with bortezomib treatment is thought to be due to a reversible effect on megakaryocyte platelet production rather than a direct cytotoxic effect. While the exact mechanism of bortezomib-induced thrombocytopenia remains unknown, it is thought that proteasome inhibition with bortezomib prevents the activation of nuclear factor κB (NF-κB).r
Cyclic thrombocytopenia has not been linked to an increase in significant bleeding events.
Incidence/prevalence
Numerous trials report grade 3 and grade 4 thrombocytopenia occurring in 30% of patients receiving bortezomib.rr
Onset/duration
Thrombocytopenia associated with bortezomib treatment is usually transient and cyclical. Platelet nadir occurs around days 11 - 14, with a reduction of approximately 60% from baseline. Platelet counts typically recover rapidly between each treatment cycle. It is rarely severe enough to postpone subsequent cycles. There was no evidence of cumulative thrombocytopenia in the APEX trial.r