Allogeneic hematopoietic cell transplantation is equally effective in secondary acute lymphoblastic leukemia (ALL) compared to de-novo ALL—a report from the EBMT registry

Secondary acute lymphoblastic leukemia (s-ALL) comprises up to 10% of ALL patients. However, data regarding s-ALL outcomes is limited. To answer what is the role of allogeneic hematopoietic cell transplantation (HCT) in s-ALL, a matched-pair analysis in a 1:2 ratio was conducted to compare outcomes between s-ALL and de novo ALL (dn-ALL) patients reported between 2000–2021 to the European Society for Blood and Marrow Transplantation registry. Among 9720 ALL patients, 351 (3.6%) were s-ALL, of which 80 were in first complete remission (CR1) with a known precedent primary diagnosis 58.8% solid tumor (ST), 41.2% hematological diseases (HD). The estimated 2-year relapse incidence (RI) was 19.1% (95%CI: 11–28.9), leukemia-free survival (LFS) 52.1% (95%CI: 39.6–63.2), non-relapse mortality (NRM) 28.8% (95%CI: 18.4–40), GvHD-free, relapse-free survival (GRFS) 39.4% (95%CI: 27.8–50.7), and overall survival (OS) 60.8% (95%CI: 47.9–71.4), and did not differ between ST and HD patients. In a matched-pair analysis, there was no difference in RI, GRFS, NRM, LFS, or OS between s-ALL and dn-ALL except for a higher incidence of chronic GvHD (51.9% vs. 31.4%) in s-ALL. To conclude, patients with s-ALL who received HCT in CR1 have comparable outcomes to patients with dn-ALL.