Long-term follow-up of clonal evolution under treatment by lenalidomide. Sequential samples of BM mononuclear cells were collected from 18 responder patients. Results from 4 patients with loss of efficacy or AML transformation (A) and 4 still responders (B) are shown. Other results from 10 additional patients are available in supplemental Figure 3. Depth at the variant position was considered to calculate variant allele frequency and its 95% CI. For each patient, variant allele frequencies of a given mutation were compared between 2 consecutive time points (indicated in months) of the follow-up period using Fisher’s exact test. *P < .05; **P < .01; ***P < .001. Closed symbols represent dominant mutations and open symbols represent minor mutations.