Radiation dosimetry considerations of locoregional radionuclide cancer therapy

Radiation dosimetry allows for the estimation of potential efficacy and toxicity in locoregional radionuclide cancer therapy (LRCT). In order to evaluate and compare candidate radiopharmaceuticals, models that encompass the range of expected activity distributions in the tumor were examined to estimate the radiation-absorbed doses to tumor and to the tissues surrounding the tumor as a function of depth. These models were executed for the clinically relevant tumor/source volumes, and Monte Carlo radiation transport simulations were performed with 23 radionuclides that are commercially available and relevant in theranostics. This allows for the comparison of tumor dosimetry and depth dosimetry of the various available radionuclides to aid the clinician in the selection of the most appropriate nuclide for specific locoregional therapy cases. Empirical modeling of the volume-normalized results was also performed in order to provide the clinician with simple tools to quickly compare and evaluate the use of different radionuclides. Utility of these models is illustrated by providing an example of their use in an animal case utilizing LRCT.