Modeling of treatment response to erythropoiesis-stimulating agents as a function of center- and patient-related variables: results from the Anemia Cancer Treatment (ACT) study.

BACKGROUND In anemic cancer patients treated with erythropoiesis-stimulating agent (ESA), (i) to examine the proportion of variance in hemoglobin (Hb) outcomes attributable to patients versus center, country, and region and (ii) to develop predictive models of treatment response. METHODS Retrospective study with a minimum of three visits at 1-month intervals. Three hundred and seven centers in 13 European countries contributed 2192 anemic ESA-treated cancer patients. Treatment response criteria included: Hb increase > or =1 g/dl, Hb increase > or =1 g/dl within 8 weeks, hematopoietic response (Hb increase > or =2 g/dl or Hb > or = 12 g/dl), Hb increase > or =2 g/dl, and Hb between 12 and 13 g/dl. RESULTS Hb increased from 9.54 +/- 0.95 g/dl (baseline) to 10.88 +/- 1.49 g/dl (visit 3). Hb change from visits 1 to 2 (index of relative immediacy of response to ESA) averaged 0.81 +/- 1.17 g/dl. The proportion of variance in Hb outcomes attributable to center was 11.8%-34.3%, country 2.9%-20.7%, and region 0.0%-7.6%. Immediacy of response to ESA was the most prevalent predictor of treatment response, followed by diagnosis of hematological malignancy and age <70 years. CONCLUSIONS . Hb outcomes are determined significantly by the treating center and less so by country or region. The remaining majority variance was attributable to patient-related factors. Immediacy of response to ESA is the single most important predictor of treatment. When used according to guidelines, ESAs are effective in managing anemia in cancer patients and improving treatment outcomes.