Pre-therapeutic blood dosimetry in patients with differentiated thyroid carcinoma using 124-iodine: predicted blood doses correlate with changes in blood cell counts after radioiodine therapy and depend on modes of TSH stimulation and number of preceding radioiodine therapies

• Published in: Annals of nuclear medicine Vol. 26; no. 9; pp. 723 - 729
• Main Authors: Hartung-Knemeyer, Verena, Nagarajah, James, Jentzen, Walter, Ruhlmann, Marcus, Freudenberg, Lutz S., Stahl, Alexander R., Bockisch, Andreas, Rosenbaum-Krumme, Sandra J.
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.11.2012; Springer Nature B.V
• Subjects: Adult; Aged; Aged, 80 and over; Blood Cell Count; Female; Humans; Imaging; Iodine Radioisotopes - therapeutic use; Male; Medicine; Medicine & Public Health; Middle Aged; Nuclear Medicine; Original Article; Radiology; Radiometry; Radionuclide Imaging; Radiotherapy Dosage; Risk; Thyroid Neoplasms - blood; Thyroid Neoplasms - diagnostic imaging; Thyroid Neoplasms - radiotherapy; Thyrotropin - blood; Thyrotropin - pharmacology; Young Adult; Bone marrow toxicity; 124-I; Changes in blood cell counts; Radioiodine therapy; Blood dosimetry
• ISSN: 0914-7187; 1864-6433
• DOI: 10.1007/s12149-012-0632-1

Objective Pre-therapeutic blood dosimetry prior to a high-dose radioiodine therapy (RAIT) is recommended and a blood dose of 2 Gy is considered to be safe. In this study, changes in the blood cell count after radioiodine therapy of high risk differentiated thyroid carcinoma (DTC) were analyzed and compared with the results of the pre-therapeutic blood dosimetry using 124 I. Moreover, the influence of different modes of TSH stimulation and the number of preceding radioiodine therapies on the blood dose were assessed. Methods 198 patients with locally advanced or metastasized DTC received a pre-therapeutic blood dosimetry using 124 I. To analyze the influence of the modes of TSH stimulation and the number of preceding RAITs on blood dose subgroups were built as follows: patients with endogenous TSH stimulation versus patients with exogenous TSH stimulation and patients with no preceding RAIT versus patients with at least one preceding RAIT. In 124/198 patients subsequent RAIT was performed. In 73/124 patients, hemograms were performed from day 2 to 12 month after RAIT. Results There was no high-grade bone marrow toxicity (i.e. ≥grade 3) in patients receiving less than 2 Gy blood dose—independent of the therapeutic history. Within the first month after radioiodine therapy, there was an overall decrease in the white blood cell and platelet counts. The erythrocyte count was essentially stable. There was a correlation between cell count decrease and predicted blood doses (Spearman’s correlation coefficient >−0.6 each) for the white cell line and the platelets. With regard to the subgroups, the blood dose per administered 131 I activity (BDpA) was significantly higher in patients with endogenous TSH stimulation (median 0.08 Gy/GBq) than in patients with exogenous TSH stimulation (0.06 Gy/GBq) and in patients with no previous RAIT (0.08 Gy/GBq) compared to patients who had previously undergone at least one RAIT (0.07 Gy/GBq). Conclusions The range of BDpA among DTC patients is rather wide. Our results suggest that lower blood doses can be expected when using exogenous TSH stimulation and blood doses are generally higher at first RAIT compared to subsequent RAITs. Thus, we advise to make blood dosimetry standard praxis prior to a high-activity RAIT.