Gemtuzumab ozogamicin with or without interleukin 11 in patients 65 years of age or older with untreated acute myeloid leukemia and high-risk myelodysplastic syndrome: comparison with idarubicin plus continuous-infusion, high-dose cytosine arabinoside

We investigated treatment with gemtuzumab ozogamicin (GO) in 51 patients aged 65 years or older with newly diagnosed acute myeloid leukemia (AML), refectory anemia (RA) with excess of blasts in transformation, or RA with excess blasts. GO was given in doses of 9 mg/m(2) of body-surface area on days 1 and 8 or, therapeutically equivalently, on days 1 and 15, with or without interleukin 11 (IL-11; 15 microg/kg per day on days 3 to 28), with assignment to IL-11 treatment made randomly. Complete remission (CR) rates were 2 of 26 (8%) for GO without IL-11 and 9 of 25 (36%) for GO with IL-11. Regression analyses indicated that IL-11 was independently predictive of CR but not survival. We compared GO with or without IL-11 with idarubicin plus cytosine arabinoside (IA), as previously administered, in similar patients. The CR rate with IA was 15 of 31 (48%), and survival was superior with IA compared with GO with or without IL-11 (P =.03). Besides accounting for possible covariate effects on outcome, we also accounted for possible trial effects (TEs) arising because IA and GO with or without IL-11 were not arms of a randomized trial. Bayesian posterior probabilities that GO with or without IL-11 produced longer survival than IA, after accounting for covariates and TEs, were less than 0.01 in patients with abnormal cytogenetic findings (AC) and less than 0.15 in patients with normal cytogenetic findings (NC). Regarding CR, the analogous probabilities were less than 0.02 for GO without IL-11 (all cytogenetic groups), and for GO with IL-11, less than 0.25 for AC groups and about 0.50 for NC groups. TEs 2 to 5 times the magnitude of those previously observed would be needed to conclude that survival with GO with or without IL-11 is likely longer than with IA. Thus, there is little evidence to suggest that GO with or without IL-11 should be used instead of IA in older patients with newly diagnosed AML or myelodysplastic syndrome.