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August 06, 2019
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Rituximab maintenance confers lasting PFS benefit for patients with follicular lymphoma

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Rituximab maintenance following induction immunochemotherapy conferred durable PFS compared with observation among patients with follicular lymphoma, according to long-term results of the randomized phase 3 PRIMA study published in Journal of Clinical Oncology.

Researchers did not, however, observe an OS benefit after 9 years of follow-up.

“The primary analysis from PRIMA demonstrated prolonged PFS with rituximab maintenance when applied after first-line immunochemotherapy induction to patients with previously untreated, high-tumor-burden follicular lymphoma,” Emmanuel Bachy, MD, PhD, assistant professor in the department of hematology at University of Lyon in France, and colleagues wrote. “This long-term follow-up strengthens these previously published results, demonstrating significantly longer PFS, time to next anti-lymphoma treatment, and time to next chemotherapy treatment in the rituximab maintenance arm compared with the observation arm.”

Bachy and colleagues also reported a final evaluation of the safety of rituximab (Rituxan, Genentech) maintenance.

The open-label, multicenter PRIMA trial included 1,018 patients with untreated follicular lymphoma who responded to one of three first-line, rituximab-based immunochemotherapy induction regimens. Researchers randomly assigned patients to 2 years of rituximab maintenance (n = 505; median age, 55 years; range, 22-84) at 375 mg/m2 once every 8 weeks or observation (n = 513; median age, 57 years; range, 26-79).

The extended follow-up included 309 patients in the maintenance group and 298 patients in the observation group who gave consent.

PFS and OS served as the study’s primary endpoints. Time to next anti-lymphoma treatment and time to next chemotherapy treatment served as secondary endpoints.

Median duration of follow-up was 9 years (range, 0-11.5) from randomization.

Results showed median PFS of 10.5 years in the maintenance group compared with 4.1 years in the observation group (HR = 0.61; 95% CI, 0.52-0.73).

Researchers noted no significant difference in OS between the groups (HR = 1.04; 95% CI, 0.77-1.4), with 10-year OS estimates of 79.9% with observation and 80.1% with rituximab maintenance.

By data cutoff, 88 patients in the maintenance group and 84 patients in the observation group had died, most of disease progression.

Median time to next anti-lymphoma treatment was not reached in the maintenance group compared with 6.1 years in the observation group (HR = 0.66; 95% CI, 0.55-0.78). Median time to next chemotherapy treatment also was not reached in the maintenance group compared with 9.3 years in the observation group (HR = 0.71; 95% CI, 0.59-0.86).

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Researchers observed no new safety signals with rituximab maintenance. Grade 3 to grade 4 adverse events appeared more common in the maintenance vs. observation group and included cytopenias (5.2% vs. 1.6%) and infections (4.4% vs. 1%).

“This 9-year follow-up of the PRIMA study demonstrates that rituximab maintenance after induction immunochemotherapy provides significant long-term PFS benefit over observation,” Bachy and colleagues wrote. “Despite the lack of OS advantage, it is noteworthy that more than half of the patients in the rituximab arm remain free of disease progression and have not required new anti-lymphoma treatment beyond 10 years.”– by John DeRosier

Disclosures: Bachy reports honoraria from, consultant/advisory roles with and/or travel expenses from Amgen, Gilead Sciences, Janssen and Roche. Please see the study for all other authors’ relevant financial disclosures.