The INSPIRE clinical trial – Dosimetry of radioiodine therapy for thyroid cancer patients in the UK


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Jan Taprogge1, Carla Abreu1, Lily Carnegie-Peake1, Paul Gape1, Dominic Rushforth1, Charlotte Barker1, Antigoni Divoli1, Jonathan Gear1, Lucy McAreavey1, Iain Murray1, Brenda Pratt1, Bruno Rojas1, Allison Craig1, Lenka Vavrova1, Kee Howe Wong1, Kate Newbold1, Glenn Flux1
1Royal Marsden NHS Foundation Trust

Abstract

Background

Investigating National Solutions for Personalised Iodine-131 Radiation Exposure (INSPIRE, ClinicalTrials.gov Identifier: NCT04391244) aims to determine the range of radiation doses delivered to organs-at-risk and healthy organs to develop improved risk estimates from radioiodine therapy. Furthermore, the study investigates the possibility of a threshold absorbed dose required for successful ablation of the thyroid remnant in thyroid cancer patients following thyroidectomy.


Method

The bio-distribution and pharmacokinetic parameters of radioiodine in patients enrolled in the study will be assessed using a series of SPECT-CT and whole-body scans. Scans will be quantified and the amount of radioiodine activity remaining in thyroid remnant and normal tissues determined. Participants are enrolled with a single or multiple image acquisition time points following the administration of radioiodine [131I]NaI. Radiation doses to the thyroid remnant are measured employing maximum voxel dosimetry and using the MIRD formalism. An in-house developed 3D voxel dosimetry package  is used to determine radiation doses to healthy organs. In patients enrolled with a single image acquisition time point, population half-lives are employed to estimate pharmacokinetic parameters and time integrated activities.


Results

To date, 23 patients have been enrolled in the study at the Royal Marsden Hospital, including 10 multiple-scan patients with a minimum of three imaging time points. Maximum absorbed doses to the thyroid remnants varied considerably from < 1 to 28 Gy. In all patients, whole-body, lung and bone absorbed doses were found to be < 0.1 Gy.

Conclusion

Initial results from the INSPIRE clinical dosimetry study have already shown the wide range of radiation doses delivered. The study aims to recruit a total of 50 patients and is currently being set up as a multi-centre UK study. The network will serve as a basis for further multi-centre clinical trials that can include a dosimetry component.

Acknowledgments: The MEDIRAD project has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 755523.

Impact statement

The results of the INSPIRE clinical trial could potentially allow for personalised treatment planning when using radioiodine for thyroid cancer.