Short Course of Bendamustine and Rituximab Followed By 90Y-Ibritumomab Tiuxetan in Patients with Chemotherapy-Naïve Follicular Lymphoma: Results of Fol-Brite
Authors: Lansigan Frederick , Zaki Bassem I , Yen Stephanie P , Winer Eric S , Ryan Helen , Findley Darcie L , Metzler Sara R , Shaw Lynn , Tsui Annie , MacKenzie Todd , Beaven Anne W 
Published: October 2019

Abstract
Background:
Y90 Ibritumumab tiuxetan (90YIT) is approved for use for follicular lymphoma (FL) patients (pts) who have achieved a complete or partial response to frontline chemotherapy; however, its use after bendamustine and rituximab (BR) has never been studied. 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. In this prospective, single-arm, open-label, multicenter phase II trial, we assessed the response rate and safety of a short induction course of BR for 4 cycles followed by consolidation with 90YIT for chemotherapy-naïve pts with FL.
Methods:
Consenting pts greater than 18 years with chemotherapy naïve FL (grade 1-2 and 3a) requiring treatment were eligible for this study. All pts had Stage II-IV disease and had adequate hematologic, liver, and renal function.
Treatment consisted of an initial dose of rituximab 375mg/m2. One week later, bendamustine 90mg/m2 was administered on days 1 and 2, and rituximab 375mg/m2 was given on day 1. BR was given for 4 cycles every 28 days. Pts were restaged 4-6 weeks after the last dose of BR. Pts were considered 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 give 6-12 weeks after completion of the last cycle of BR. The primary endpoint of this study 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:
Forty-two pts were enrolled in this study: 38 pts initiated study treatment, and 4 were screen failures. Median age was 58 years [range 31-74]. The study enrolled FLIPI low (18%), intermediate (47%), high (34%) risk pts; 32 of 38 (84%) were Grade 1-2 and 6 (16%) were Grade 3a.
Response rates after 4 cycles of BR: Thirty-eight pts have completed 4 cycles of BR and 38 are evaluable for response. Twenty-two of 38 evaluable pts achieved a CR/CRu (58%) and 15 of 38 pts had a PR (39%) for an overall response rate (ORR) of 97%. One pt had stable disease (SD).
Response rates after BR followed by 90YIT: Thirty of 38 BR-treated pts have received 90YIT and are evaluable for the primary endpoint of CR/CRu. Of the 38 BR treated pts, two in CR were unable to receive 90YIT due low platelets, one was not eligible to receive 90YIT due to achievement of SD only, one declined treatment, and four are not yet evaluable for response. Twenty-five of 30 evaluable pts are in CR/CRu (83%), 4 remain in PR (13%) after 90YIT and one progressed during 90YIT, for an ORR of 96%. Of the 14 pts who had a PR after BR, 7 (50%) converted to a CR/CRu immediately after 90YIT, with three (21%) additional conversions to CR/CRu in follow-up, the latest occurring 16 months after 90YIT.
Grade 3-4 hematologic toxicities during BR included: lymphopenia (36%), neutropenia (8%), thrombocytopenia (3%), leukopenia (3%). Non-hematologic toxicities included grade 2 phlebitis (14%) and grade 3 hyperglycemia (8%), hyponatremia (3%), diarrhea (3%), infusion-related reaction (3%), headache (3%), rectal hemorrhage (3%).
Grade 3-4 hematologic toxicities after 90YIT included: neutropenia (33%), leukopenia (36%), thrombocytopenia (36%), lymphopenia (14%), anemia (3%). Non-hematologic toxicities included skin infection (3%). Median neutrophil recovery was 8 weeks [range 8 to 12] and median platelet recovery was 9 weeks [range 5 to 36] after Y90IT.
There have been no incidences of neutropenic fever. One pt developed chronic myelogenous leukemia, occurring 11 months after treatment with BR followed by Y90-IT. There have been no cases of myelodysplasia or acute myelogenous leukemia.
Conclusions:
In this nearly final analysis, the CR/CRu rate of pts completing all study therapy (BR followed by 90YIT) is 83%, the ORR is 96%, and the conversion rate from PR to CR/CRu is 71%. We conclude that sequential treatment with BR followed by Y90IT is highly effective and safe, and should be considered as a frontline treatment option for FL.

Disclosures
Lansigan: Teva Pharmaceuticals: Research Funding; Spectrum Pharmaceuticals: Research Funding.