Renal uptake of bismuth-213 and its contribution to kidney radiation dose following administration of actinium-225-labeled antibody

Phys Med Biol. 2011 Feb 7;56(3):721-33. doi: 10.1088/0031-9155/56/3/012. Epub 2011 Jan 10.


Clinical therapeutic studies using (225)Ac-labeled antibodies have begun. Of major concern is renal toxicity that may result from the three alpha-emitting progeny generated following the decay of (225)Ac. The purpose of this study was to determine the amount of (225)Ac and non-equilibrium progeny in the mouse kidney after the injection of (225)Ac-huM195 antibody and examine the dosimetric consequences. Groups of mice were sacrificed at 24, 96 and 144 h after injection with (225)Ac-huM195 antibody and kidneys excised. One kidney was used for gamma ray spectroscopic measurements by a high-purity germanium (HPGe) detector. The second kidney was used to generate frozen tissue sections which were examined by digital autoradiography (DAR). Two measurements were performed on each kidney specimen: (1) immediately post-resection and (2) after sufficient time for any non-equilibrium excess (213)Bi to decay completely. Comparison of these measurements enabled estimation of the amount of excess (213)Bi reaching the kidney (γ-ray spectroscopy) and its sub-regional distribution (DAR). The average absorbed dose to whole kidney, determined by spectroscopy, was 0.77 (SD 0.21) Gy kBq(-1), of which 0.46 (SD 0.16) Gy kBq(-1) (i.e. 60%) was due to non-equilibrium excess (213)Bi. The relative contributions to renal cortex and medulla were determined by DAR. The estimated dose to the cortex from non-equilibrium excess (213)Bi (0.31 (SD 0.11) Gy kBq(-1)) represented ∼46% of the total. For the medulla the dose contribution from excess (213)Bi (0.81 (SD 0.28) Gy kBq(-1)) was ∼80% of the total. Based on these estimates, for human patients we project a kidney-absorbed dose of 0.28 Gy MBq(-1) following administration of (225)Ac-huM195 with non-equilibrium excess (213)Bi responsible for approximately 60% of the total. Methods to reduce renal accumulation of radioactive progeny appear to be necessary for the success of (225)Ac radioimmunotherapy.

MeSH terms

  • Actinium / adverse effects
  • Actinium / chemistry*
  • Animals
  • Antibodies / administration & dosage*
  • Antibodies / chemistry*
  • Autoradiography
  • Biological Transport
  • Bismuth / metabolism*
  • Female
  • Humans
  • Kidney / metabolism*
  • Kidney / pathology
  • Kidney / radiation effects*
  • Mice
  • Mice, Inbred BALB C
  • Radiation Dosage
  • Radioisotopes / metabolism*
  • Radiometry


  • Antibodies
  • Radioisotopes
  • Actinium
  • Bismuth