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SELIMETRY-a multicentre I-131 dosimetry trial: a clinical perspective.

ABSTRACT: Treatment options for patients with thyroid cancer that is no longer sensitive to iodine therapy are limited. Those treatments which currently exist are associated with significant toxicity. The SELIMETRY trial (EudraCT No 2015-002269-47) aims to investigate the role of the MEK inhibitor Selumetinib in resensitizing advanced iodine refractory differentiated thyroid cancer to radioiodine therapy. Patients deemed to have sufficient iodine uptake in previously iodine refractory lesions after 4 weeks of Selumetinib therapy will be given an empirical activity of 5.5?GBq I-131, and response to therapy will be assessed. The trial presents an opportunity to investigate the dosimetric aspects of radioiodine therapy for advanced thyroid cancer. Patients will undergo serial I-123 single-photon emission CT (SPECT)/CT scans following Selumetinib therapy to determine whether there has been a change in the degree of iodine uptake to justify further I-131 therapy, and to allow dosimetric calculations to predict absorbed dose to target lesions following therapy. Patients receiving I-131 therapy will undergo a further series of post-therapy SPECT/CT scans to allow dosimetric calculations. We describe the challenges in setting up a multicentre trial in a relatively underinvestigated field, describing the work that has been carried out to calibrate and validate measurements to ensure that standardized image data are collected at each site. We hope that this trial will lead to individualization and optimization of therapy for patients with advanced thyroid cancer and that the ground work carried out in setting up a network of centres capable of standardized molecular radiotherapy dosimetry will lead to further clinical trials in this field.

SUBMITTER: Wadsley J

PROVIDER: S-EPMC5605100 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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SELIMETRY-a multicentre I-131 dosimetry trial: a clinical perspective.

Wadsley Jonathan J Gregory Rebecca R Flux Glenn G Newbold Kate K Du Yong Y Moss Laura L Hall Andrew A Flanagan Louise L Brown Sarah R SR

The British journal of radiology 20170314 1073

Treatment options for patients with thyroid cancer that is no longer sensitive to iodine therapy are limited. Those treatments which currently exist are associated with significant toxicity. The SELIMETRY trial (EudraCT No 2015-002269-47) aims to investigate the role of the MEK inhibitor Selumetinib in resensitizing advanced iodine refractory differentiated thyroid cancer to radioiodine therapy. Patients deemed to have sufficient iodine uptake in previously iodine refractory lesions after 4 week ...[more]

PMID: 28291381

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Project description:PurposeApproximately 50% of head and neck cancer (HNC) patients will experience loco-regional disease recurrence following initial courses of therapy. Retreatment with external beam radiotherapy (EBRT) is technically challenging and may be associated with a significant risk of irreversible damage to normal tissues. Radiopharmaceutical therapy (RPT) is a potential method to treat recurrent HNC in conjunction with EBRT. Phantoms are used to calibrate and add quantification to nuclear medicine images, and anthropomorphic phantoms can account for both the geometrical and material composition of the head and neck. In this study, we present the creation of an anthropomorphic, head and neck, nuclear medicine phantom, and its characterization for the validation of a Monte Carlo, SPECT image-based, 131 I RPT dosimetry workflow.Methods3D-printing techniques were used to create the anthropomorphic phantom from a patient CT dataset. Three 131 I SPECT/CT imaging studies were performed using a homogeneous, Jaszczak, and an anthropomorphic phantom to quantify the SPECT images using a GE Optima NM/CT 640 with a high energy general purpose collimator. The impact of collimator detector response (CDR) modeling and volume-based partial volume corrections (PVCs) upon the absorbed dose was calculated using an image-based, Geant4 Monte Carlo RPT dosimetry workflow and compared against a ground truth scenario. Finally, uncertainties were quantified in accordance with recent EANM guidelines.ResultsThe 3D-printed anthropomorphic phantom was an accurate re-creation of patient anatomy including bone. The extrapolated Jaszczak recovery coefficients were greater than that of the 3D-printed insert (∼22.8 ml) for both the CDR and non-CDR cases (with CDR: 0.536 vs. 0.493, non-CDR: 0.445 vs. 0.426, respectively). Utilizing Jaszczak phantom PVCs, the absorbed dose was underpredicted by 0.7% and 4.9% without and with CDR, respectively. Utilizing anthropomorphic phantom recovery coefficient overpredicted the absorbed dose by 3% both with and without CDR. All dosimetry scenarios that incorporated PVC were within the calculated uncertainty of the activity. The uncertainties in the cumulative activity ranged from 23.6% to 106.4% for Jaszczak spheres ranging in volume from 0.5 to 16 ml.ConclusionThe accuracy of Monte Carlo-based dosimetry for 131 I RPT in HNC was validated with an anthropomorphic phantom. In this study, it was found that Jaszczak-based PVCs were sufficient. Future applications of the phantom could involve 3D printing and characterizing patient-specific volumes for more personalized RPT dosimetry estimates.

Project description:IntroductionCLR1404 is a theranostic molecular agent that can be radiolabeled with 124I (CLR 124) for positron emission tomography (PET) imaging, or 131I (CLR 131) for single-photon emission computed tomography (SPECT) imaging and targeted radionuclide therapy. This pilot study evaluated a pretreatment dosimetry methodology in a triple-negative breast cancer patient who was uniquely enrolled in both a CLR 124 PET imaging clinical trial and a CLR 131 therapeutic dose escalation clinical trial.Materials and methodsThree-dimensional PET/CT images were acquired at 1, 3, 24, 48, and 120 h postinjection of 178 MBq CLR 124. One month later, pretherapy 2D whole-body planar images were acquired at 0.25, 5, 24, 48, and 144 h postinjection of 370 MBq CLR 131. Following the therapeutic administration of 1990 MBq CLR 131, 3D SPECT/CT images were acquired at 74, 147, 334, and 505 h postinjection. The therapeutic CLR 131 voxel-level absorbed dose was estimated from PET (RAPID PET) and SPECT (RAPID SPECT) images using a Geant4-based Monte Carlo dosimetry platform called RAPID (Radiopharmaceutical Assessment Platform for Internal Dosimetry), and region of interest (ROI) mean doses were also estimated using the OLINDA/EXM software based on PET (OLINDA PET), SPECT (OLINDA SPECT), and planar (OLINDA planar) images.ResultsThe RAPID PET and OLINDA PET tracer-predicted ROI mean doses correlated well (m ≥ 0.631, R2 ≥ 0.694, p ≤ 0.01) with both the RAPID SPECT and OLINDA SPECT therapeutic mean doses. The 2D planar images did not have any significant correlations. The ROI mean doses differed by -4% to -43% between RAPID and OLINDA/EXM, and by -19% to 29% between PET and SPECT. The 3D dose distributions and dose volume histograms calculated with RAPID were similar for the PET/CT and SPECT/CT.ConclusionsThis pilot study demonstrated that CLR 124 pretreatment PET images can be used to predict CLR 131 3D therapeutic dosimetry better than CLR 131 2D planar images. In addition, unlike OLINDA/EXM, Monte Carlo dosimetry methods were capable of accurately predicting dose heterogeneity, which is important for predicting dose-response relationships and clinical outcomes.

Dataset Information

SELIMETRY-a multicentre I-131 dosimetry trial: a clinical perspective.

Publications

SELIMETRY-a multicentre I-131 dosimetry trial: a clinical perspective.

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