Retrospective Analysis of Clinical Factors Relating to the Outcome of Gemtuzumab Ozogamicin Therapy

It is difcult to predict the clinical outcome of gemtuzumab ozo- gamicin (GO) therapy based solely on the previously identified predictive factors. We retrospectively analyzed the relationship between clinical factors and outcomes in 12 patients with relapsed or refractory acute leukemia who received GO monotherapy. The median patient age at initial GO infusion was 56 years, and the average initial dosage was 8.1 mg/m 2 . Four patients (33%) achieved an overall remission (OR) . The time from diagnosis to GO infusion was signicantly longer in patients with OR than in patients with no remission (NR)(1747 vs. 501 days, respectively ; P < 0.01) . The number of karyotype abnormalities before GO infusion was signicantly greater in NR patients (9.5) than in OR patients (0.5 ; P = 0.03) . Monocyte counts in the bone marrow before GO therapy were signicantly lower in OR than in NR patients (100/ µL vs. 1080/μL, respectively ; P = 0.048) . In a multivariate analysis, monocyte count was signicantly associated with overall survival (P = 0.005) . CD14 expression in OR patients was lower than in NR patients, with the exception of 4 patients whose French-American-British subtypes were M4 or M5 (OR, 0.3% ; NR, 2.5% ; P = 0.04) . NR was noted in all 6 patients who underwent allogeneic stem cell transplantation before and/or after GO infusion. Patients showing good sensitivity to conventional chemotherapy with good survival after diagnosis tend to be sensitive to GO as well. A low monocyte count in the bone marrow at infusion of GO might indicate improved efcacy of GO therapy. Further investigation is warranted for establishing appropriate patient selection and for clarifying efcient conditions for GO therapy.