Prognostic impact of prevalent chronic lymphocytic leukemia stereotyped subsets: Analysis within prospective clinical trials of the German CLL Study Group

Almost one-third of all patients with chronic lymphocytic leukemia (CLL) express stereotyped B-cell receptor immunoglobulins (BcR IG) and can be assigned to distinct subsets, each with a particular BcR IG. The largest stereotyped subsets are #1, #2, #4 and #8, associated with specific clinico-biological characteristics and outcomes in retrospective studies. We assessed the associations and prognostic value of these BcR IG in prospective multicenter clinical trials reflective of two different clinical situations: (i) early-stage patients ('watch and wait' arm of the CLL1 trial) (n=592); (ii) patients in need of treatment, enrolled in three phase III trials (CLL8, CLL10, CLL11), treated with different chemo-immunotherapies (n=1,861). Subset #1 was associated with del(11q), higher CLL International Prognostic Index (CLL-IPI) scores and similar clinical course to CLL with unmutated immunoglobulin heavy variable (IGHV) genes (U-CLL) in both early and advanced stage groups. IGHV-mutated (M-CLL) subset #2 cases had shorter time-to-first-treatment (TTFT) versus other M-CLL cases in the early-stage cohort (hazard ratio [HR]: 4.2, confidence interval [CI]: 2-8.6, P<0.001), and shorter time-to-next-treatment (TTNT) in the advancedstage cohort (HR: 2, CI: 1.2-3.3, P=0.005). M-CLL subset #4 was associated with lower CLL-IPI scores and younger age at diagnosis; in both cohorts, these patients showed a trend towards better outcomes versus other MCLL. U-CLL subset #8 was associated with trisomy 12. Overall, this study shows that major stereotyped subsets have distinctive characteristics. For the first time in prospective multicenter clinical trials, subset #2 appeared as an independent prognostic factor for earlier TTFT and TTNT and should be proposed for risk stratification of patients.