The outcome of Chronic lymphocytic leukaemia patients with 97% IGHV gene identity to germline is distinct from cases with <97% identity and similar to those with 98% identity.

IGHV gene mutational status has prognostic significance in chronic lymphocytic leukaemia ( CLL) but the percentage of mutations that correlates best with clinical outcome remains controversial. We initially studied 558 patients from diagnosis and found significant differences in median time to first treatment ( TTFT) among Stage A patients and in overall survival ( OS) for the whole cohort, between cases with <97% and 97-98·99% identity and between cases with 97-98·99% and ≥99% identity, when cases from the IGHV3-21 Stereotype Subset #2 were excluded. A significant difference in progression-free survival (PFS) and OS between those with <97% and 97-98·99% identity, but not between those with 97-98·99% and ≥99% identity was also observed in a validation cohort comprising 460 patients in the UK CLL4 trial. Cox Regression analyses in the Stage A cohort revealed that a model which incorporated <97%, 97-98·99% and ≥99% identity as subgroups, was a better predictor of TTFT in CLL than using the 98% cut-off. Multivariate analysis selected the three mutational subgroups as independent predictors of TTFT in Stage A patients, and of OS in the diagnostic cohort. This study highlights that cases with 97% identity should not be considered to have the same prognosis as other cases with mutated IGHV genes defined as <98% identity to germline. [ABSTRACT FROM AUTHOR]