Clonal evolution during treatment with ibrutinib. (A) A swimmer plot of 15 patients who progressed on ibrutinib. Each lane represents an individual patient. Numbers at the end of the line indicate TTP (months). Open diamonds indicate BTK and PLCG2 candidate regions were tested for mutations, and no mutation was detected. Red triangles indicate the detection of BTK mutations. Blue triangles indicate PLCG2 mutations. (B) Growth kinetics of mutant clones. Three representative cases with BTK and/or PLCG2 mutations are shown (PD8, PD9, and PD11). Red color indicates BTK mutation. Blue color indicates PLCG2 mutation. The cell count of mutant clones was estimated from the VAF assessed by ddPCR (supplemental Table 2), the ALC, and the proportion of B cells (CD19⁺). Time points with VAFs below the lowest limit of detection (0.2%) are plotted as 1 cell (10°).