8061 Background: Classification and regression tree (CART) and multiple regression (MR) methods can be used to model BL characteristics of pts treated with DA (Aranesp®) relative to their performance on hematologic and clinical endpoints. Methods: Data from an open-label, multicenter study (SOAR) of DA 3.0 mcg/kg Q2W dosed to week (wk) 15 in pts with CIA were used in this exploratory analysis. Endpoints included % transfused from wks 5 -17, hemoglobin (Hb) change at wk 17, and ≥ 3 point FACT-Fatigue change (clinically meaningful improvement) at wk 17. MR models allow for assessment of a covariate after adjusting for the effects of other important covariates. Relative to MR, CART is more flexible in handling missing data and in discovering interactions among covariates. Results: This analysis includes data from all 1558 pts enrolled. Overall, using intent-to-treat methods, the mean (95% CL) change in Hb (n = 1462) was 1.7 (1.6, 1.8) g/dL with over 70% of pts achieving a hematopoietic response (Hb ≥ 12 g/dL or ≥ 2 g/dL rise from BL). The Kaplan-Meier % (95% CL) of pts transfused was 19% (17, 21) overall. Mean (95% CL) change in FACT-Fatigue score was 4.7 (4.1, 5.3). Statistically significant covariates by MR are shown (table). The more anemic pts were at BL, the more likely a higher Hb change would occur; the more fatigued pts were at BL, the more likely a 3-point change in FACT-Fatigue would occur. Breast and lymphoid cancer pts responded well relative to lung cancer pts, although this may be related to factors such as gender, chemotherapy, and disease stage. Ferritin and serum erythropoietin levels (after adjusting for tumor type and BL Hb or FACT-Fatigue) were also significant but less impactful covariates. Conclusions: Response to erythropoietic therapy in pts with CIA is significantly impacted by BL Hb category and tumor type. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Amgen, Inc. Amgen, Inc. Amgen, Inc. Amgen, Inc. Amgen, Inc.