Short Course of Bendamustine and Rituximab Followed By 90Y-Ibritumomab Tiuxetan in Patients with Chemotherapy-Naive Follicular Lymphoma (FOL-BRITe): Final Report of Response Rates and Progression Free Survival
Authors: Costa Cristiana A , Zaki Bassem I , Yen Stephanie P , Winer Eric S , Ryan Helen , Findley Darcie , Metzler Sara R , Shaw Lynn , Tsui Annie , MacKenzie Todd A , Beaven Anne W , Lansigan Frederick 
Published: October 2019

Abstract
Background:
Y90-Ibritumomab tiuxetan (90YIT) is approved for use for follicular lymphoma (FL) patients who have achieved a complete or partial response to frontline chemotherapy; however, its use after bendamustine and rituximab (BR) has not been reported. BR has proven to be a superior frontline therapy over R-CHOP in the treatment of FL and is a widely used initial treatment strategy. This analysis focuses on the long-term outcomes and safety of untreated follicular lymphoma patients treated with a short induction course of BR for 4 cycles followed by consolidation with 90YIT.
Methods:
Patients greater than 18 years with chemotherapy-naïve FL (grade 1-2 and 3a) requiring treatment were eligible. All patients had Stage II-IV disease and had adequate hematologic, liver, and renal function. Treatment consisted of an initial dose of rituximab 375 mg/m2. One week later, bendamustine 90 mg/m2 was administered on days 1 and 2, and rituximab 375 mg/m2 was given on day 1. BR was given for 4 cycles every 28 days. Patients were restaged 4-6 weeks after the last dose of BR. Patients were eligible for consolidation with 90YIT if they obtained at least a partial response after induction, had a platelet count greater than 100,000/mm3, a granulocyte count greater than 1,500/mm3, and bone marrow infiltration less than 25%. 90YIT was given 6-12 weeks after completion of the last cycle of BR. The primary endpoint is complete and unconfirmed complete response (CR/CRu) rate after sequential therapy with BR followed by 90YIT. Secondary endpoints are overall response rate after 4 cycles of BR, conversion rate from partial response (PR) after BR to CR/CRu after 90YIT, progression-free survival, and safety. The 1999 NHL Working Group Criteria was used to assess response.
Results:
From October 2010 to May 2014, forty-four patients were enrolled in this study (NCT01234766). 39 patients initiated treatment, and 5 were screen failures. Median age was 57 years [range 31-75]. The study enrolled FLIPI low (18%), intermediate (44%), and high (38%) risk patients; 33 of 39 (85%) were Grade 1-2 and 6 (15%) were Grade 3a.
Twenty-two of 39 patients achieved CR/CRu (56%) and 16 of 39 patients had a PR (41%) for an overall response rate (ORR) of 97%. One patient had stable disease (SD). Four patients were not randomized to receive 90YIT: one in CR and one in PR were unable to receive 90YIT due to thrombocytopenia, one only achieved SD after BR, and one declined treatment. Thirty of 35 evaluable patients were in CR/CRu (86%), 4 remained in PR (11%) after 90YIT and one progressed during 90YIT, for an ORR of 97%. The number of patients in PR after BR who reached CR/CRu immediately after 90YIT were 10 of 16 (63%). Three (19%) additional patients converted to CR/CRu during follow-up, the latest occurring 16 months after 90YIT.
After a median follow up of 30 months, 25 patients (71%) remain in CR/CRu, 10 patients (29%) have progressed/relapsed with a 24-month PFS of 80% (95% CI 63-90) [Figure]. The median PFS was not reached.
Grade 3-4 hematologic toxicities during the 90YIT period included: neutropenia (34%), leukopenia (37%), thrombocytopenia (40%), lymphopenia (15%), and anemia (6%). There were no incidences of febrile neutropenia. One patient developed JC Virus/Progressive Multifocal Leukoencephalopathy, 13 months after receiving the last dose of rituximab and 90YIT on study. One patient developed chronic myeloid leukemia 11 months after, one patient developed acute myeloid leukemia 15 months after, and one patient developed uterine cancer 52 months after all study treatment. One patient died to progression of the lymphoma, 35 months after treatment. There have been no reported cases of myelodysplasia.
Conclusions:
In this 2.5 year report of patients that received BR followed by 90YIT, the CR/CRu rate of patients completing all study therapy is 71% and the 24-month PFS is 80%. There is a high rate of conversion in partial responders to CR/CRu (81%), some occurring more than one year after treatment with 90YIT. The durable PFS is comparable to what is reported in the FIT trial (Morschhauser et al. JCO 2013) and the phase II Spanish intergroup study (Canales et al. ASH 2013). BR followed by 90YIT is a well-tolerated regimen for follicular lymphoma with high response rates that is a safe and highly effective as first-line therapy. Long-term safety reflects the natural history of patients with indolent lymphomas.
Figure Figure.

Disclosures
Lansigan: Pharmacyclics: Consultancy; Teva: Research Funding; Celgene: Consultancy; Spectrum: Consultancy, Research Funding.