BTK and B-cell chronic lymphocytic leukemia: In addition, data from a mutation analysis study of 63 patients who were still on ibrutinib after 3 years in an early-access program at 29 French centers revealed detection of BTK and PLCG2 mutations in 57% and 13% of the next-generation sequencing samples (n=30) and the authors reported that after a median follow-up of 8.5 months from sample collection, the presence versus the lack of a BTK mutation was significantly associated with subsequent CLL progression [27].