Swimmer’s plot showing MRD status until last assessment and timing of delayed rituximab (◇), next treatment (▴), or death (×). Letters to the left of the swimmer’s plot indicate which patients had mutations in MAP2K (M), TP53 (T), or expressed unmutated IGHV4-34 immunoglobulin rearrangements (V). TP53 and MAP2K mutations are listed in Table 2. Patient #2 was not characterized molecularly. Patient #19 became MRD-negative in blood (blue) after delayed rituximab, just before date cutoff. BM, bone marrow.