Results of the Interim Analysis of the “HUSOM” Trial: Hungarian Study of Maintenance After Rituximab Pretreatment, A Multicentre, Phase III, Open-Label Study Evaluating the Benefit of a Long-Term MabThera (rituximab) Maintenance Therapy in Patients with Advance Follicular Lymphoma After Induction of Response (CR(u) or PR) with a MabThera (rituximab)-Containing First Line Regimen
Authors: Schneider Tamas J. , Rosta Andras , Losonczy Hajna , Radvanyi Gaspar , Ujj Gyorgy , Illes Arpad , Jakucs János , Borbenyi Zita 
Published: October 2019

Abstract
Abstract 2714

Background:
The addition of immunotherapy–rituximab–to the treatment regimen of follicular lymphomas has led to a significant improvement in therapeutic efficacy. In the mid-2000's, immuno-chemotherapy was approved by European authorities as part of the induction treatment for untreated and relapsed follicular lymphomas followed by maintenance therapy. Data about efficacy and safety of rituximab maintenance following first-line induction with R-CVP or R-CHOP have not been available. Therefore the Hungarian National Working-Group initiated a trial: Hungarian Study of Maintenance after Rituximab Pretreatment. Methods: Between July 2005 and December 2008 126 newly diagnosed patients with follicular lymphoma who had achieved partial or complete remission after induction treatment with either R-CVP or R-CHOP were treated with two years of rituximab maintenance. In this open-label, single-arm study rituximab was administered in standard dose (375 mg/m2) every 8 weeks, 12 times in total.

Results:
126 patients have been included. Data of 99 patients are available for this interim analysis. Average age of the 30 male (30%) and 69 female (70%) patients were 53.2 (29–80) years. Histological subtypes were grade-1 in 32% of patients, grade-2 in 49%, and grade-3a in 19%. Twenty-eight percent of patients had tumors with size over 7 cm. Sixty-four percent of patients were in the moderate risk group (FLIPI: 1–2) and 36% in the high risk group. Fifty-six percent of patients received R-CVP and 44% R-CHOP induction treatment. After induction 61% achieved complete remission and 39% partial remission. With respect to induction treatment regimen, patients treated with R-CVP 52% showed CR and 48% PR. In patients treated with R-CHOP 75% had CR and 25% had PR. Fourteen patients (37%) in PR converted to CR during or after rituximab maintenance therapy. Three-year OS after initiation of maintenance was 94%, EFS was 84%, and PFS was 88%. With respect to FLIPI, OS rates were 97% and 89% for moderate and high risk groups respectively. Patients treated with R-CHOP achieved significantly better PFS (98% vs. 80%; p=0.0096) and EFS (93% vs. 76%; p=0.0332) than those treated with R-CVP. Patients achieving CR compared to PR showed significantly higher PFS (100% vs. 68 %; p<0.0001) and EFS (95 % vs. 65 %; p<0.0001) values respectively. Safety: Four patients experienced SAEs. Three patients died (due to causes other than lymphoma). Two hepatitis B reactivations occurred.

Conclusion:
These data confirm that rituximab maintenance is a safe and effective treatment for patients after induction with rituximab based immuno-chemotherapy. Interestingly those patients who were treated with more intense induction regimen R-CHOP and those who achieved a better remission status seemed to have a favorable outcome. Thirty-seven percent of patients receiving rituximab maintenance converted from PR to CR. Therefore these data support the use of rituximab maintenance in 1st line treatment.

Disclosures:
No relevant conflicts of interest to declare.