Adaptive biokinetic modelling of iodine-131 in thyroid cancer treatments: implications on individualised internal dosimetry

Abstract

Nowadays therapies involving radioiodine (I-131) represent 84% of the total metabolic treatments in Europe, according to the last report of the European Association of Nuclear Medicine in relation to treatment planning for molecular radiotherapy. Last recommendations of the European Council, i.e. 2013/59/Euroatom, mandates that metabolic treatments should be planned according to the radiation doses delivered to individual patients, analogous to external beam radiotherapy. In this work, we present a novel biokinetic model for I-131 that allows on to obtain realistic activity distributions for particular patients with thyroid cancer in absence of metastasis. Other models existing in the literature present either a too simple metabolic description to obtain realistic results or a too complex one for adapting the model to individual patients, and many of these models are not indicated for metabolic treatments. The individualisation of activity distribution is obtained by an optimisation method that adjusts our model to a set of experimental measurements. Significant differences in terms of absorbed doses are observed between our model and the standard generalist models, especially in terms of red marrow absorbed dose.

Association Between Radioactive Iodine Treatment for Pediatric and Young Adulthood Differentiated Thyroid Cancer and Risk of Second Primary Malignancies

“…Salivary gland, stomach, urinary bladder, and kidney are estimated to be highly exposed from RAI therapy for DTC (absorbed doses > 1 Gy for 100 mCi administered activity; Data Supplement) owing to the ability of these and other nearby organs and tissues to concentrate RAI. 38 , 52 , 53 RAI therapy was associated with a two-fold risk of cancer of the salivary gland, which is highly radiosensitive, 54 consistent with previous studies. 6 , 7 , 17 , 20 Although stomach and urinary bladder are also radiosensitive, 54 , 55 the kidney appears to be less so.…”

Biokinetic model of radioiodine I-131 in nine thyroid cancer patients subjected to in-vivo gamma camera scanning: A simplified five-compartmental model

“…As clearly depicted, the biological half-lives of the whole body fluctuated in the range of 6~30h, except for one patient with renal failure syndrome listed in Willegaignon's clinical case report, where this value was equal to 45.5h [15]. Noteworthy is that Chen et al adopted a similar method to survey the biokinetic model of five thyroid cancer patients and reported that the biological half-life of either whole body or thyroid was 12.5±5.5 or 15.8±24.0h [5]; whereas Guiu-Souto et al adopted the initial values of 6 and 480h, respectively, in their iterative fitting algorithm based on the theoretical simulation of HMA using a similar assumption in the ICRP-53 report [19]. However, due to the normal metabolic mechanism in the HMA thyroid gland, the fact that the latter holds the radioiodine for a relatively long time seems to be quite realistic.…”

“…analytical assessments listed in Table 3 were made based on the exponential decay of two compartments and defined as instant or slow decay terms for the numerical analysis [15][16][17][18]20]. The most intricate model of Guiu-Souto et al [19] included ten compartments and assigned two feedback paths (from body fluid to stomach and liver to body fluid), whereas others either had no assigned feedback path or defined only one feedback path. Meanwhile, a short biological half-life of the whole body reported by Guiu-Souto et al [19] can be attributed to a nonequilibrium status with the daughter compartment (thyroid) in their unique biokinetic model.…”

“…The most intricate model of Guiu-Souto et al [19] included ten compartments and assigned two feedback paths (from body fluid to stomach and liver to body fluid), whereas others either had no assigned feedback path or defined only one feedback path. Meanwhile, a short biological half-life of the whole body reported by Guiu-Souto et al [19] can be attributed to a nonequilibrium status with the daughter compartment (thyroid) in their unique biokinetic model. Thus, the daughter compartment (thyroid) dominated the whole decay characteristic.…”

Development of a Compartmental Pharmacokinetic Model for Molecular Radiotherapy with 131I-CLR1404

“…These tabulated values serve as the basis for the well-established MIRD formalism, a dosimetric methodology based on the use of non-individualized dose-activity coefficients that is widespread both in therapy and diagnostic applications [13]. In this regard, several biokinetic models of radiopharmaceuticals have been developed, both for therapy and radiation protection applications [14][15][16][17][18][19][20].…”