Prior studies have investigated patients' characteristics, treatments, and outcomes for older adults with myelodysplastic syndromes, but most failed to distinguish chronic myelomonocytic leukemia. Recognizing potentially important differences between the diseases, we undertook a population-based comparison of baseline characteristics, treatments, and outcomes between older adults with chronic myelomonocytic leukemia and myelodysplastic syndromes. The patients' data were obtained from Surveillance Epidemiology and End Results registry data from 2001-2005, linked to Medicare claims. Baseline characteristics, treatment (red blood cell transfusions, hematopoietic growth factors, hypomethylating agents, chemotherapy or transplantation), progression to acute myeloid leukemia, and overall survival were compared using bivariate techniques. Multivariate logistic regression estimated differences in treatments received. Cox proportional hazard models estimated the effects of chronic myelomonocytic leukemia relative to myelodysplastic syndromes on progression-free survival. A larger proportion of patients with chronic myelomonocytic leukemia (n=792), compared to patients with myelodysplastic syndromes (n=7,385), failed to receive any treatment (25% versus 15%; P<0.0001), or only received red blood cell transfusions (19.8% versus 16.7%; P=0.037). A larger percentage of patients with chronic myelomonocytic leukemia progressed to acute myeloid leukemia (42.6% versus 15.5%, respectively; P<0.0001), with shorter time to progression. Chronic myelomonocytic leukemia patients had a shorter median survival (13.3 versus 23.3 months; P<0.0001) and lower 3-year survival rate (19% versus 36%; P<0.0001). Adjusted estimates, controlling for baseline characteristics and selected treatments, indicate that chronic myelomonocytic leukemia was associated with an increased risk of progression to acute myeloid leukemia or death (HR 2.22; P<0.0001), compared to myelodysplastic syndromes. In conclusion, chronic myelomonocytic leukemia is less frequently treated in older adults and is associated with worse outcomes, even after controlling for the patients' baseline characteristics and selected treatments. Our data suggest the need for continued evaluation of the biological differences between these diseases and clinical trials targeting chronic myelomonocytic leukemia.
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