Allogeneic haematopoietic stem cell transplantation improves outcome of adults with relapsed/refractory Philadelphia chromosome-positive acute lymphoblastic leukemia entering remission following CD19 chimeric antigen receptor T cells.

Relapsed/refractory Philadelphia chromosome-positive acute lymphoblastic leukemia (r/r Ph+ ALL) has an extremely poor prognosis. Chimeric antigen receptor T-cell (CART) therapy has acquired unprecedented efficacy in B-cell malignancies, but its role in the long-term survival of r/r Ph+ ALL patients is unclear. We analyzed the effect of CART on 56 adults with r/r Ph+ ALL who accepted split doses of humanized CD19-targeted CART after lymphodepleting chemotherapy. 51/56 (91.1%) achieved complete remission (CR) or CR with inadequate count recovery (CRi), including 38 patients with negative minimal residual disease (MRD) tested by bone marrow BCR-ABL1 copies. Subsequently, 30/51 CR/CRi patients accepted consolidative allogeneic haematopoietic stem cell transplantation (alloHSCT). Their outcomes were compared with those of 21/51 contemporaneous patients without alloHSCT. The 2-year overall survival (OS) and leukemia-free survival (LFS) of CR/CRi patients with alloHSCT were significantly superior to those without alloHSCT (58.9%, CI 49.8-68.0% vs. 22.7%, CI 12.7-32.7%, p = 0.005; 53.2%, CI 43.6-62.8% vs. 18.8%, CI 9.2-28.4%, p = 0.000, respectively). Multivariate analysis revealed that alloHSCT and MRD-negative post-CART were the independent prognostic factors for OS and LFS. CART therapy is highly effective for r/r Ph+ ALL patients, and consolidative alloHSCT could prolong their OS and LFS.