Outcome of relapsed or refractory acute B-lymphoblastic leukemia patients and BCR-ABL positive blast cell crisis of B-lymphoid lineage with extramedullary disease receiving inotuzumab ozogamicin

Acute lymphoblastic leukemia (ALL) can relapse in the extramedullary compartment, with or without medullary involvement. Response to treatment may be unique. We evaluated response to inotuzumab ozogamicin (INO) in 31 relapsed/refractory (r/r) BALL patients with extramedullary disease (EMD). Median age was 31 (range, 19-81) years. All patients were heavily pretreated, including allogeneic hematopoietic stem cell transplantation (allo-HCT; n=18). Overall response rate after two INO cycles was 84% (complete remission (CR), 55%; partial remission (PR), 29%; resistant disease (PD), 13%; early death, 3%). Median follow-up was 29 months and median overall survival (OS) 12.8 months. One-year and 2-year OS rates were 53% (95%-CI, 37-76%) and 18% (95%-CI, 8-43%), respectively. Age had no impact on OS when assessed as a continuous variable or dichotomized at 60 years. Twelve patients proceeded to allo-HCT (CR, n=6; PR, n=3; PD, n=3). Prior to allo-HCT, eight patients received ≤2 and four patients 3-4 INO cycles. Sinusoidal obstruction syndrome was reported in three patients, including one after transplant. Allo-HCT evaluated as a time-dependent variable had no impact on OS. INO seems to be effective as debulking strategy in r/r-ALL with EMD. However, INO followed by allo-HCT seems not to be effective in maintaining long term disease control.