Among people treated with blinatumomab for acute lymboblastic leukemia (ALL), higher CD19 expression, as well as prior history of extramedullary-ALL (EM-ALL), were linked with development of EM-ALL upon treatment failure, according to a study involving 65 individuals.

Participants had refractory/relapsed ALL and were treated with blinatumomab. Investigators looked for predictors of leukemia response, relapse, and resistance. Among the results:

• The complete remission rate was 51%.
• Those with high leukemia burden, history of prior EM-ALL, or active EM-ALL when initiating blinatumomab were less likely to achieve complete remission.
• Among refractory cases, 41% had evidence of EM-ALL progression.
• CD19 expression was negative in 18% of these cases; it was dim in 23%.
• Among responders, 61% relapsed; EM-ALL relapse occurred in 4 in every 10 of those who relapsed.
• CD19 expression was negative in 35% of evaluable responders; it was dim in 6%.
• Overall and event-free survival were improved for patients who underwent allogeneic HCT.
• Overall survival was superior for patients who responded to blinatumomab.