Commentary on Abstract #432

March 1, 1999

In general, rituximab has an acceptable toxicity profile. However, as the drug has been used more widely, new side effects have been identified that warranted a modification of the package insert. Approximately 70 serious infusion-related events have been reported, with 8 fatalities out of an estimated14,000 patients treated. Death was associated with bronchospasm, hypotension, and severe respiratory distress, with no clear predisposing factors.

In general, rituximab has an acceptable toxicity profile. However, as the drug has been used more widely, new side effects have been identified that warranted a modification of the package insert. Approximately 70 serious infusion-related events have been reported, with 8 fatalities out of an estimated14,000 patients treated. Death was associated with bronchospasm, hypotension, and severe respiratory distress, with no clear predisposing factors.

In addition, a small number of patients treated with rituximab at a time when they had bulky disease and circulating tumor cells developed thrombocytopenia, a rapid decrease in tumor load, and a number of electrolyte abnormalities consistent with tumor lysis, but not clearly a tumor lysis syndrome (Byrd et al, abstract #432; Byrd et al: J Clin Oncol, vol 17, 1999 [in press]). In general, tumor lysis in indolent disorders cannot be readily predicted (Cheson et al: J Clin Oncol 16:2313-2320, 1998) or prevented. Rapid intervention is most important for a successful outcome.