Tumoral fibrosis effect on the radiation absorbed dose of 177Lu–Tyr3-octreotate and 177Lu–Tyr3-octreotate conjugated to gold nanoparticles

• Fibrosis increases the radiation absorbed dose to the tumor.
• Fibrosis increases the radiopharmaceutical residence time in the tumor.
• The multimeric nature of the radiopharmaceuticals enhances the radiopharmaceutical retention.

The aim of this work was to evaluate the tumoral fibrosis effect on the radiation absorbed dose of the radiopharmaceuticals 177Lu–Tyr3-octreotate (monomeric) and 177Lu–Tyr3-octreotate–gold nanoparticles (multimeric) using an experimental HeLa cells tumoral model and the Monte Carlo PENELOPE code. Experimental and computer micro-environment models with or without fibrosis were constructed. Results showed that fibrosis increases up to 33% the tumor radiation absorbed dose, although the major effect on the dose was produced by the type of radiopharmaceutical (112 Gy-multimeric vs. 43 Gy-monomeric).