Chemoimmunotherapy With Fludarabine (F), Cyclophosphamide (C), and Rituximab (R) (FCR) Versus Bendamustine and Rituximab (BR) In Previously Untreated and Physically Fit Patients (pts) With Advanced Chronic Lymphocytic Leukemia (CLL): Results Of a Planned Interim Analysis Of The CLL10 Trial, An International, Randomized Study Of The German CLL Study Group (GCLLSG)

FCR is the current standard first line treatment regimen in advanced CLL (Hallek et al., Lancet, 2010), but is associated with significant side effects. The GCCLSG initiated an international phase III study in order to test the non-inferiority regarding efficacy and potentially better tolerability of BR compared to FCR in first-line therapy of physically fit pts without del(17p).

688 CLL pts from 158 sites in five countries (Germany, Austria, Switzerland, Denmark and Czech Republic) were screened centrally for immunophenotype, genomic aberrations by FISH, IGHV sequenzing, comorbidity burden and renal function. 564 CLL pts with CIRS score ≤ 6, creatinine clearance > 70 ml/min and without del(17p) were enrolled between October 2008 and June 2011. Pts were randomly assigned to receive 6 courses of either FCR (N= 284; F 25mg/m² i.v. d1–3, C 250 mg/m² i.v. d1–3, R 375 mg/m² i.v. d 0 at first cycle and 500 mg/m² d1 all subsequent courses; q 28 days) or BR (N=280; B 90mg/m² i.v. d1+2, R 375 mg/m² i.v. d 0 at first cycle and 500 mg/m² d1 all subsequent courses; q 28 days). The intent-to-treat population consisted of 561 pts, because three patients were excluded due to deferred treatment (1 pt decision, 1 treatment before randomization, 1 misdiagnosis).

22 % were Binet A, 38 % Binet B and 40 % Binet C. The median age was 62 years (yrs) (range 33 to 82), median CIRS score 2 (range 0-6). There were significantly more pts with unmutated IGVH in the BR arm (68%) in comparison to the FCR arm (55%; p=0.003). All other characteristics including median age were well balanced.

A mean number of 5.27 courses was given in the FCR arm versus 5.41 courses in the BR arm (p=0.022). 70.6% (FCR) and 80.3% (BR) of pts received 6 courses (p=0.008). Dose was reduced by more than 10% in 27.3% (FCR) and 31.6% (BR) of all courses given (p = 0.012).

The median observation time was 27.9 months (mo) in all pts alive. While response evaluation was missing in 14 pts, 547 pts (274 FCR; BR 273) were evaluable for response and all 561 pts (282 FCR; 279 BR) for progression-free survival (PFS), event-free survival (EFS) and OS. The overall response rate was identical in both arms with 97.8% (p=1.0). The complete response rate (CRR) (confirmed by central immunhistology) with FCR was 47.4% as compared to 38.1% with BR (p=0.031). MRD data were available at interim analysis from 192 pts (99 FCR; 93 BR) of the first 300pts. 71.7% of pts in the FCR and 66.7% in the BR arms achieved MRD-levels below 10^-4 in peripheral blood at final staging (p=0.448). The complete MRD data set will be available by November. PFS was 85.0% at 2 yrs in the FCR arm and 78.2% in the BR arm (p=0.041). EFS was 82.6% at 2 yrs in the FCR arm and 75.7% in the BR arm (p=0.037).There was no difference in OS rate for the FCR vs BR arm (94.2% vs 95.8% at 2 years p=0.593). Hazard Ratio for PFS, EFS and OS was 1.385, 1.375 and 0.842 respectively. PFS was assessed in pts < 65 yrs and ≥ 65 yrs. While there was a significant difference in pts < 65 yrs between both treatment arm (median PFS for BR 36.5 mo vs not reached for FCR; p=0.016), the difference disappeared in elderly pts (not reached vs. 45.6 mo; p=0.757). A multivariate analysis including treatment arm, Binet stage, age, sex, comorbidity, serum TK, serum beta2-microglobulin (Beta2M), del(11q) and IGHV status identified treatment arm, Beta2M, del(11q) and IGHV as independent prognostic factors for PFS and EFS.

FCR treated pts had significantly more frequent severe, CTC grade 3 to 5, adverse events during the whole observation period (90.8% vs 78.5%; p<0.001). Especially severe hematotoxicity was more frequent in the FCR arm (90.0% vs 66.9%, p<0.001). The higher rate of severe neutropenia (81.7% vs 56.8%, p<0.001) resulted in a significantly higher rate of severe infections (39.0% vs 25.4%, p=0.001) in the FCR arm, especially in the elderly (FCR: 47.4% vs BR: 26.5%; p=0.002). Treatment related mortality occurred in 3.9% (n=11) in the FCR and 2.1% (n=6) in the BR arm.

The results of this planned interim analysis show that FCR seems more efficient than BR in the first-line treatment of fit CLL pts with regard to higher CRR, as well as longer PFS and EFS. These advantages might be balanced by a higher rate of severe adverse events, in particular neutropenia and infections, associated with FCR. In light of these results, no firm recommendation of one regimen over the other can be given at the present time regarding the first-line use in CLL pts with good physical fitness.

Eichhorst:Roche: Consultancy, Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding. Gregor:Roche: Consultancy, Honoraria, Travel Support Other; Mundipharma: Travel Support, Travel Support Other. Plesner:Mundipharma: Research Funding. Trneny:Roche: Honoraria, Research Funding. Fischer:Roche: Travel grants Other; Mundipharma: Travel grants, Travel grants Other. Kneba:Roche: Consultancy, Research Funding. Wendtner:Roche: Consultancy, Research Funding; Mundipharma: Consultancy, Research Funding. Kreuzer:Roche: Honoraria; Mundipharma: Honoraria. Stilgenbauer:Roche: Consultancy, Research Funding, Travel grants Other; Mundipharma: Consultancy, Research Funding. Böttcher:Roche: Honoraria, Research Funding. Hallek:Janssen: Research Funding; Gilead: Research Funding; Roche: Research Funding.