medwireNews: Treatment with obinutuzumab-based chemotherapy prolongs progression-free survival over rituximab-based therapy in patients with follicular lymphoma, GALLIUM trial data suggest.
Robert Marcus (King’s College Hospital, London, UK) and study co-authors explain: “Obinutuzumab […] is a glycoengineered type II anti-CD20 monoclonal antibody that has lower complement-dependent cytotoxicity than rituximab but greater antibody-dependent cellular cytotoxicity and phagocytosis and greater direct B-cell killing effects.”
They investigated whether these characteristics improved outcome in 1202 treatment-naïve patients with CD20-positive follicular lymphoma.
During a median follow-up of 34.5 months, disease progression, relapse, or death occurred in 16.8% of 601 patients randomly assigned to receive intravenous infusions of obinutuzumab 1000 mg on days 1, 8, and 15 of cycle 1 and on day 1 of 6 or 8 subsequent cycles, followed by up to 2 years of maintenance.
This was significantly lower than the rate of 24.0% observed in the 601 patients randomly assigned to receive rituximab 375 mg/m2 on day 1 of each cycle.
Overall, the risk for progression, relapse, or death was a significant 34% lower with obinutuzumab than with rituximab, and at 3 years the estimated progression-free survival rates were 80.0% and 73.3%, respectively.
By contrast, overall response rates at the end of induction therapy were similar between the two treatments, at 88.5% in the obinutuzumab group and 86.9% in the rituximab group.
This suggests that “the advantage of obinutuzumab in prolonging remission appears to be related to the maintenance treatment,” say James Armitage (University of Nebraska, Omaha, USA) and Dan Longo (Brigham and Women’s Hospital, Boston, Massachusetts, USA) in an editorial that accompanies the research published in The New England Journal of Medicine.
They add that “there might be no advantage for an obinutuzumab-containing chemoimmunotherapy regimen if maintenance treatment was not planned.”
Marcus et al report that overall survival was also similar between the two groups; 35 (5.8%) patients died in the obinutuzumab group compared with 46 (7.7%) in the rituximab group. The estimated 3-year overall survival rates were 94.0% and 92.1%, respectively.
Adverse events were “consistent with the known safety profiles of the trial treatments,” say the researchers, and were more common in the obinutuzumab group than in the rituximab group, with grade 3 to 5 events occurring in 74.6% and 67.8%, respectively. The rate of fatal toxic effects, however, was similar between the groups, at 4.0% versus 3.4%.
Discussing the findings, Armitage and Longo point out that the two treatments were given at different doses even though ”there was no evidence” to suggest that “the antibodies differ in target affinity.”
Therefore “it is possible that giving rituximab at a dose of 1000 mg might reduce or eliminate any difference in progression-free survival — that is, if the difference is primarily a dose effect,” they remark.
“At the moment, the competition between these agents looks too close to call,” Armitage and Longo conclude.
By Laura Cowen
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