Thrombocytopenia is a reduction in the normal levels of functional platelets. It is associated with bortezomib treatment, particularly in patients who have had a number of prior therapies. However, it is rarely severe enough to postpone subsequent cycles.
Thrombocytopenia associated with bortezomib treatment is thought to be due to a reversible effect on megakaryocyte platelet production rather than a direct cytotoxic effect. The thrombocytopenia was not associated with an increase in significant bleeding events in the trial.
In the APEX trial, grade 3 and grade 4 thrombocytopenia occurred in 30% of patients receiving bortezomib.r
Thrombocytopenia associated with bortezomib treatment is usually transient and cyclical. Platelet nadir occurs around day 11 with a reduction of approximately 60% from baseline. Platelet counts usually recover towards the end of the rest period of each treatment cycle. There was no evidence of cumulative thrombocytopenia in the APEX trial.r