Description of the cohort and most proximal immunotherapy. (A) CONSORT diagram showing patients with LS identified via multicenter retrospective analysis. (B) Map illustrating countries from which cases of LS were submitted. Quantity of cases reported per country represented by colored shading. (C) Percentage of LS cases reported with baseline cytogenetics incorporating a KMT2Ar (at diagnosis or preimmunotherapy relapse). (D) Summary of most proximal immunotherapy administered before development of LS. (E) Sequencing of various immunotherapeutic agents received. #E-069 and E-080 had blinatumomab and inotuzumab within the same time frame. ∗Indicates when therapy was initiated for post-HSCT relapse. (F) Summary of all antigen-targeted therapies received. ∗Indicates most proximal therapy received, ˆindicates alternative CD19 targeting with an antibody-drug conjugate (ADC). Blina, blinatumomab; HSCT, hematopoeitic stem cell transplant; Ino, inotuzumab; MDS, myelodysplastic syndrome.