The absolute percent deviation of IGHV mutation rather than a 98% cut off predicts survival of chronic lymphocytic leukaemia patients treated with fludarabine, cyclophosphamide and rituximab
The degree of somatic hypermutation, determined as percent deviation of immunoglobulin heavy chain gene variable region sequence from the germline (IGHV% is an important prognostic factor in chronic lymphocytic leukaemia (CLL) Currently, a cut off of 2% deviation or 98% sequence identity to germline in IGHV sequence is routinely used to dichotomize CLL patients into mutated and unmutated groups. Because dissimilar IGHV% cut offs of 1 5% were identified in different studies, we wondered whether no cut off should be applied and IGHV% treated as a continuous variable. We analysed the significance of IGHV% in 203 CLL patients enrolled on the original frontline fludarabine, cyclophosphamide and rituximab (FCR) trial with a median of 10 years follow up. Using the Cox Proportional Hazard model, IGHV% was identified as a continuous variable that is significantly associated with progression free (PFS) and overall survival (OS) (P 0*001) Furthermore, we validated this finding in 323 patients treated with FCR off protocol and in the total cohort (n 535) Multivariate analysis revealed a continuous trend. Higher IGHV% levels were incrementally associated with favorable PFS and OS in both FCR treated cohorts (P 0*001, both cohorts) Taken together, our data suggest that IGHV% is a continuous variable in CLL patients treated with FCR.
British journal of haematology