engleski

Gimme five

Aim: The aim of this study was to derive and compile the data from the very few dosimetric contributions in the literature on thyroid stunning, in order to propose novel practical guidelines for postsurgical application of radioiodine-131 in thyroid cancer patients. Material and Methods: A non-linear regression modelling was used to fit the curves representing the extent of thyroid stunning in dependence on the radiation absorbed dose of diagnostic I-131, as derived from the paper by Jeevanram et al. (Nucl Med Biol, 1986) (1) and the abstracts by Medvedec et al. (Eur J Nucl Med, 2000) (2) and Sinyuta et al. (Eur J Nucl Med, 2001) (3). The regression curves were fitted by using the mean values given for three (1, 2) and four (3) groups of patients, as well as the values given for further seven individual patients (1). Results: According to the regression models, there is no thyroid stunning only if the radiation absorbed dose of diagnostic I-131 delivered to the residual thyroid tissue is about 5 Gy or less. Thyroid stunning significantly increases above the cut-off absorbed dose of 10 Gy (2, 3) and 17 Gy (1) and amounts to about 50% or more. Diagnostic activity of 74 MBq I-131 usually produces severe thyroid stunning (1, 2, 3). Somehow similar data, i.e. 74 MBq I-131 and 6 Gy, has been suggested in the abstract by Behr et al. (J Nucl Med 2001) too. Conclusion: From the latest dosimetric advances on thyroid stunning, we recommend to deliver not more than 5 Gy into the target tissue and to use diagnostically 37 MBq I-131 or less before expected I-131 therapy for thyroid cancer. Otherwise, thyroid stunning may occur and an appropriate correction should be applied to take into account consequently decreased efficacy per unit therapeutic activity.

thyroid cancer; radioiodine therapy; thyroid stunning

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