By Ingrid Grasmo
Approximately 25% of patients with immune thrombocytopenia purpura (ITP) who receive treatment with rituximab maintain a treatment-free response lasting for at least 5 years, study findings suggest.
The findings are of importance, given that treatments for ITP that provide long-term therapeutic benefit without the need for continued dosing, ongoing monitoring, and side effects are limited.
"The estimated… 5-year sustained response rates help to provide clinicians and patients with realistic expectations of the long-term outcome of rituximab treatment," say Vivek Patel (Cornell University, New York, USA) and colleagues.
For the study, the researchers followed up 72 adults and 66 children (aged 17 years or younger) with ITP who received rituximab treatment and achieved either a complete response (CR; platelets >150x109/L) or partial response (PR; platelets 50-150x109/L).
All patients had baseline platelet counts below 30x109/L and received four weekly infusions of 375 mg/m2, except for 12 children who received a single infusion.
Of the 66 children with an initial response, 68% had a CR and 32% had a PR. In total, 58% sustained a platelet count of 50x109/L for at least 1 year following rituximab treatment. Further analysis showed that these children were more than 80% likely to sustain the response at 2 years, with 20 and six children achieving responses lasting 2 and 5 years, respectively.
Analysis showed that 76% of adults achieved a CR and 24% achieved a PR. Relapse was observed in 36% of adult patients, occurring at a median of 2.1 years after initial treatment.
When the team incorporated the initial overall response rates derived from published reports with the 1-year response rates from children and adults in the study, they found estimated 5-year persisting response rates of 26% and 21%, respectively.
Patients with a PR relapsed more often and earlier than those with a CR, even after a 1-year duration of response (relapse rate of 7 vs 40% for children and 31 vs 53% for adults).
None of the 138 patients in the study experienced serious or severe long-term toxicity related to B-cell depletion after rituximab, and any infusion-related reactions associated with the medication were minimized by the addition of prednisone as pretreatment.
"Further understanding of the mechanism of action of rituximab and its potential interactions with the immune system and other treatments is needed to safely maximize the number and duration of long-term responses," conclude Patel and team in Blood.
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