The INSPIRE clinical trial – Dosimetry of radioiodine therapy for thyroid cancer patients in the UK
Session type: E-poster/poster
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.
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.
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.
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.
The results of the INSPIRE clinical trial could potentially allow for personalised treatment planning when using radioiodine for thyroid cancer.