Evaluation of Alpha-Therapy with Radium-223-Dichloride in Castration Resistant Metastatic Prostate Cancer-the Role of Gamma Scintigraphy in Dosimetry and Pharmacokinetics: Beyond the Abstract

The new legislation regarding the Medical use of ionizing radiation, at least in Europe, requires dose planning and calculation in radionuclide treatments. This is very challenging with alpha-emitters which deposit their energy and show their treatment effects within a few cell diameters, i.e. micrometer distances.

The radium(Ra)-223 radioisotope emits partly (1.1%) gamma rays, which can be measured. Gamma rays have long range, i.e. meter distances and they can be measured with an external detector. Because, this percentage of gamma decay is constant, the method gives an exact estimate of alpha decay as well. The drawback of this method is a long acquisition time, such as 60 minute imaging, and rather low quality images. However, exact alpha dose measurement would require internal detectors to be placed in the patient´s bone. The radium(Ra)-223-treatment (Xofigo®) is planned to be a simple outpatient treatment with 6 injections using 4 week intervals.

In this article (1) it was demonstrated that single metastases can be evaluated and there is a variation, and therefore dose calculations are necessitated. This kind of dose monitoring can be included as a part of this Xofigo-treatment. This dose monitoring should also be part of the clinical treatment protocol in order to better understand the clinical situation in the skeleton, because the response varied from very similar absorbed radiation doses. 

Written by: Kalevi Kairemo, Docrates Cancer Center, Helsinki, Finland & MD Anderson Cancer Center, Houston, TX, USA


Reference:
  1. Kairemo K, Joensuu T, Rasulova N, Kiljunen T, Kangasmäki A. Evaluation of Alpha-Therapy with Radium-223-Dichloride in Castration Resistant Metastatic Prostate Cancer-the Role of Gamma Scintigraphy in Dosimetry and Pharmacokinetics. Diagnostics (Basel). 2015 Jul 30; 5(3): 358-368. doi: 10.3390/diagnostics5030358.

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