Treatment of Early Stage Nodal Follicular Lymphoma Using Involved-Field Radiotherapy and Rituximab: Preliminary Results of the Mir Trial (phase II study of the German Low Grade Lymphoma Study Group (GLSG))
Authors: Herfarth Klaus , Engelhard Marianne , Borchmann Peter , Hohloch Karin , Budach Volker , Viardot Andreas , Witzens-Harig Mathias , Eich Hans , Hiddemann Wolfgang , Dreyling Martin 
Published: October 2019

Abstract
Abstract 1634

Background:
The commonly recommended treatment for early stage follicular lymphoma grade 1 or grade 2 (stage I/II) is involved-field radiotherapy (IF RT). However, a prospective German trial showed improved progression free survival compared to historical data using large field radiation techniques as extended-field radiotherapy or total lymphatic irradiation (Stuschke et al, Cancer, 80, 1997). This trial led to the conclusion that large volume radiation techniques may prevent relapses of microscopic lymphatic disease and is confirmed by the a new study, which was presented at Lugano 2011 (Engelhard et al., Ann Oncol, 22 Suppl4, 2011). However, those extensive radiation protocols are associated with significant toxicities, especially grade 3 and grade 4 adverse events concerning the hematopoietic system. It has been shown that the CD20 antibody Rituximab also has an anti lymphoma activity in CD20 positive follicular lymphoma. It might prevent out field recurrences in case of involved field radiotherapy. The German Low Grade Lymphoma Study Group (GLSG) and the German Radiation Oncology Group (ARO) of the German Cancer Society conducted a prospective, multicenter phase II trial investigating the efficacy and toxicity of a combined involved-field radiotherapy in combination with Rituximab treatment (MIR = MabThera and Involved field Radiotherapy) with an accrual of 85 patients (ClinicalTrials.gov Identifier: NCT00509184).

Patients and Methods:
85 patients (47 male / 38 female) with early stage CD20 positive follicular lymphoma grade 1/2 were included in the trial at 16 German centers between February 2007 and October 2010. Median age at diagnosis was 55 years (21–75 years). Stage I disease was diagnosed in 48 patients and Stage II in 37 patients. Macroscopically left lymphoma after diagnostic surgery was observed in 55 patients, no macroscopic lymphoma in 26 patients and an equivocal status (e.g. due to postoperative tissue changes) in 4 patients. The treatment included a first block of Rituximab (4 weekly cycles; 375 mg/m2body surface), a 4 week treatment gap with a restaging CT / planning CT of the involved region in week 7 and followed by another block of Rituximab(4 weekly cycles) concurrently with an IF RT of 40 Gy for macroscopic tumor or 30 Gy in case of a complete remission (CR). The fractionation schedule was 5×2Gy per week. Primary endpoint of the study was progression free survival (PFS) at 2 years. Secondary endpoints were CR rate after Rituximab monotherapy (week 7) and after complete treatment (week 18). Additional endpoints were relapse rate, relapse pattern, overall survival, toxicity and quality of life. The protocol was approved by the ethics committee of the University of Heidelberg Medical School and the Paul-Ehrlich-Institute (PEI-registration number 432/06). The trial was in accordance to the Declaration of Helsinki. Recruitment was finished in October 2010. Clinical report form (CRF) collection is currently under way.

Results:
The treatment was well tolerated. There were 16 serious adverse events (SAE; toxicity grade 3 or higher): 3 infections, 1 hypersensitivity, 2 cardiac disorders, 1 vascular disorder, 1 respiratory disorder, 2 gastrointestinal disorders, 4 bone injuries. Two patients died due to secondary neoplasm. 3/16 were considered to be related to the treatment. Eight patients had to be excluded from the primary response evaluation due to failed inclusion criteria (e.g. stage, histology.) or early withdrawal of their consent. The mean follow-up of the remaining 78 patients has been 22.3 +/− 11.4 months, so far. Of 55 patients with remaining macroscopic lymphoma at inclusion, 26% showed a CR at week 7 after 4 cycles Rituximab (15% missing, CRF data still have to be collected). The CR rate improved to 60% at week 18 at the first follow-up examination at week 18 (15% of data still missing) and to 80% at month 6 (22% of data still missing). A total of 8 relapses have been detected (1 infield relapse) so far. The 2 years actuarial progression free survival and overall survival has been estimated to be 90% and 96%, respectively.

Conclusion:
The combination of Rituximab and IF RT in early stage nodal follicular lymphoma grade 1/2 is well tolerated and shows promising initial results. So far, 2 years PFS matches with that of large field radiotherapy without the accompanying toxicity and is superior to historic data of IF RT only.

Disclosures:
Herfarth: Roche: Honoraria, Research Funding. Borchmann:Roche: Honoraria, Research Funding. Budach:Roche: Honoraria. Viardot:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Witzens-Harig:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Hiddemann:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Dreyling:Roche: Honoraria, Support of (other) clinical trials and Scientific Advisory Boards Other.