Favorable Toxicity Profile and Long Term Outcome of Elderly, but Physically Fit CLL Patients (pts) Receiving First Line Bendamustine and Rituximab (BR) Frontline Chemoimmunotherapy in Comparison to Fludarabine, Cyclophosphamide, and Rituximab (FCR) in Advanced Chronic Lymphocytic Leukemia (CLL): Update Analysis of an International, Randomized Study of the German CLL Study Group (GCLLSG) (CLL10 Study)

Introduction: FCR is still the standard frontline regimen for physically fit CLL pts without TP53 alteration. The international phase III CLL10 study demonstrated the inferiority of BR in comparison to FCR in this population. In order to evaluate long-term outcome and toxicity we performed an updated analysis after extended observation time.

Methods and Patients: 561 pts were randomized as previously published (Eichhorst B et al., Lancet Oncol 2016). 282 and 279 pts were randomized to receive either 6 courses of FCR or BR respectively. After the end of treatment pts were followed 3-monthly for 2 years (yrs) and 6-monthly for 3 yrs, and afterwards annually until progressive disease (PD). After PD annual visits were documented either within the study or within the registry of the GCLLSG. Health related quality of life (HRQOL) was evaluated by using the EORTC C30 questionnaire, which was completed at baseline, after 3, 6 and 12 months and then annually until year 5.

Results: After a median observation time of 58.2 months (mo) (range, 0 - 88 mo), the median progression-free survival (PFS) for FCR was 57.6 mo versus (vs) 42.3 mo for the BR arm [Hazard ratio (HR)=1.593 (95% confidence interval (CI), 1.271-1.996); p<0.0001]. While PFS was statistically significant different in younger pts [≤ 65 years (yrs)] (median PFS 57.6 vs 38.2 mo.; p< 0.0001), the difference was statistically not significant in elderly pts [> 65 yrs] (57.6 vs 42.3; p=0.134). Richter transformation (RT) was assessed as PD and occurred in 5 pts (1.8%) after FCR and 8 pts (2.9%) after BR. 77 (27.3%) pts following FCR and 108 (38.7%) following BR treatment received at least one subsequent therapy. BR was the most common second line therapy after prior FCR (42 pts), while BR re-exposure after frontline BR was performed in 31 pts. 33pts switched to FCR after BR first line therapy. So far, only 3 pts after FCR and 2 pts after BR received kinase inhibitors.

51 pts (18.1%) of the FCR arm and 54 (19.4%) pts of the BR arm deceased so far. Main cause of death in the FCR arm were secondary malignancies (14 pts; 5.0%), followed by CLL including RT (11 pts incl. 2 RT; 3.9%), infections (7 pts; 2.5%) and concomitant diseases (6 pts; 2.1%). In the BR arm CLL was the most common cause of death (15 pts incl. 6 pts with RT; 5.4%) followed by infections (12 pts; 4.3%) and concomitant disease and secondary malignancies (10 pts each; 4.3% each). Other causes of deaths were distributed similarly (incl. adverse events to frontline or relapse treatment or unknown). No differences in overall survival (OS) were observed (OS at 5 yrs, 80.9% for FCR vs 80.1% for BR; HR=1.108, 95% CI 0.755-1.627; p=0.599). The difference in OS for younger pts was statistically not significant (OS at 5-yrs 85.6% for FCR vs 81.1% for BR; p=0.119). Otherwise, 5-yrs OS was 78.8% for pts > 65 yrs receiving BR and 70.9% for those receiving FCR (p=0.238). Multivariate analysis identified treatment arm, male sex, high serum thymidine kinase (TK), del(11q) and unmuated IGHV status, but not age as independent prognostic factors for PFS. For OS only high serum TK and unmutated IGHV status were assessed as independent prognostic factors.

Secondary neoplasia was documented in 49 (17.6%) of 279 FCR treated pts and 35 (12.5%) of 278 BR treated pts. No difference in the incidence rate of secondary solid tumors was observed between both arms (for FCR 28 (10.0%) and for BR 25 (9.1%)). Secondary MDS and/or AML occurred more frequently after FCR therapy (12 [4.3%] vs 2 [0.7%]), particularly in pts >65 yrs (6 [7.0%] vs 1 [0.9%]).

540 of 561 pts (96.3%) were evaluable for HRQOL analysis, 272 pts of the FCR and 268 pts of the BR arm. No differences between both arms were detected with respect to global health status or any functional or symptom scale. As compared to an age- and sex-matched normal population functional scale values were impaired mostly during treatment phase and symptom scales also during follow-up. However, after the end of therapy and during follow-up global health status was improved.

Conclusion: Long-term follow-up data of the CLL10 study confirm the superiority of FCR regimen in young (≤ 65 yrs) and fit CLL patients. However, importantly these data support the recommendation of using BR in fit elderly pts. This particular group of pts had both a very good outcome after BR and compared to FCR a decreased risk of secondary MDS and/or AML.