Refinement of soft tissue targeting and alignment protocols in small animal radiotherapy using an injectable fiducial marker

Abstract

BioXmark® (Nanovi A/S, Denmark) is a novel injectable liquid fiducial marker (FM) that has been clinically validated to improve the delineation of tumour target volumes during radiotherapy. Similar challenges are present during preclinical radiotherapy protocols, but FMs are yet to be reverse translated back into the laboratory. Previously, BioXmark® has been reported in only one mouse study and has not yet been comprehensively assessed in animal models to demonstrate its potential within the context of the 3Rs. In this study, we aimed to evaluate the visibility, stability and radiobiological characteristics of BioXmark® in preclinical radiotherapy studies with the overall goal to improve targeting accuracy and refine existing preclinical protocols.In phantom measurements were performed to assess the CBCT imaging artefacts of BioXmark® compared to solid FMs. In vivo studies were undertaken to assess the long-term stability of BioXmark® and its impacts on tumour response. A lower GI toxicity model was developed using fractionation with the aim to reduce treatment parameters using BioXmark® to accurately target small tissue volumes. Finally, we conducted preliminary radiomics analysis to assess the feasibility of applying a radiomics approach to a subcutaneous tumour model and to measure the impact of BioXmark® on radiomics features.We found that BioXmark® is stable, well-tolerated, and detectable by CBCT at volumes ≤ 10μl. Our data show reductions in imaging artefacts of >80% compared to other solid FMs. BioXmark® had no significant effect on tumour growth delay following intra-tumoral injection. We also demonstrated the feasibility of radiomics analysis in a subcutaneous tumour model and showed that BioXmark® did not cause significant differences throughout fractionated treatment. We developed a model that recapitulates similar symptoms of clinical late-phase radiation-induced toxicity with the potential to reduce treatment parameters using BioXmark®. 2BioXmark® is superior to other FMs and can be used in preclinical radiotherapy studies to significantly refine existing protocols.

Date of Award	Jul 2022
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	National Centre for the Replacement Refinement and Reduction of Animals in Research
Supervisor	Karl Butterworth (Supervisor) & Kevin Prise (Supervisor)