[Successful treatment with blinatumomab for refractory B lymphoblastic leukemia complicated with malignant pleural effusion].

A 77-year-old man diagnosed with mixed-phenotype acute leukemia (MPAL (B/Myeloid), NOS) achieved complete remission (CR) after eight courses of hyper-CVAD/MA therapy. However, 6 months later, blasts were observed on peripheral blood smear, and bone marrow aspiration revealed that the disease had relapsed as B lymphoblastic leukemia (ALL). At this time, he had left pleural effusion. He received two courses of inotuzumab ozogamicin (InO) and achieved second hematological CR, but the left pleural effusion worsened over time, suggesting poor disease control. After changing the regimen to blinatumomab, aspiration biopsy cytology showed that the blasts in the pleural fluid disappeared and respiratory distress improved after one course of treatment. Flow cytometry results showed increased populations of CD3-positive T-cells, suggesting that blinatumomab may have migrated into the pleural fluid and exerted an antitumor effect. Although new ALL-specific antibody drugs, such as InO and blinatumomab, are expected to improve prognosis, only few reports have described their tissue migration. The difference between InO and blinatumomab in terms of efficacy of treating malignant pleural effusion remains unclear and should be explored in additional cases.