OD15 and MF66 magnetic hyperthermia treatment did not alter the blood composition, indicating a good biotolerability. The number of white blood cells (*103*μl−1), red blood cells (*106*μl−1), and the amount of hemoglobin (g*dl−1) are displayed for the magnetic hyperthermia treatment and the three control groups at 0 day, 14 days and 28 days after first hyperthermia. Black dashed lines refer to reference values (Harlan Laboratories, Venray, The Netherlands; http://www.harlan.com). MDA-MB-231 xenografts treated with MF66 (a) or OD15 (b). BxPC-3 xenografts treated with MF66 (c) or OD15 (d). Error bars indicate standard deviations. AMF alternating magnetic field, MNP magnetic nanoparticles.