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A Journal on Nuclear Medicine and Molecular Imaging

A Journal on Nuclear Medicine and Molecular Imaging
Affiliated to the Society of Radiopharmaceutical Sciences and to the International Research Group of Immunoscintigraphy
Indexed/Abstracted in: Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index (SciSearch), Scopus
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The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2015 Jan 08

language: English

Discrepant salivary gland response after radioiodine and MIBG therapies

Jentzen W., Richter M., Poeppel T. D., Schmitz J., Brandau W., Bockisch A., Binse I.

Klinik für Nuklearmedizin, Universität Duisburg-­Essen, Essen, Germany


AIM: A retrospective study using PET/CT imaging with 124I-­labeled metaiodobenzylguanidine (124I-­MIBG) was performed to estimate the (radiation) absorbed dose to the salivary glands in neuroendocrine cancer patients undergoing 131I-­MIBG therapy and to compare these results with those in radioiodine (131I-­iodide) therapy.
METHODS: Twenty-­seven patients received individual 124I-­MIBG-­PET/CT dosimetries, among whom 18 had not previously undergone any MIBG therapies (patient group before treatment) and 9 had already received MIBG therapies prior to the tracer dosimetries (patient group after treatment). For each patient, three or four 124I-­MIBG PET/CT scans were performed at approximately 4 and 24 h, as well as at approximately 48 or/and ≥96 h after tracer injection. The absorbed doses per administered 131I-­MIBG activity to the submandibular and parotid glands were calculated based on the MIRD concept, with its assumption of an uniform glandular activity distribution.
RESULTS: The mean±standard deviation of the (self-­)absorbed dose per activity averaged over both patient groups and salivary gland types was 0.53±0.24 Gy/GBq (median, 0.49 Gy/GBq; range, 0.17–1.38 Gy/GBq). The absorbed doses per activity of the patient group before treatment did not significantly deviate from those of the patient group after treatment (P=0.67). In the patient group after treatment, the mean±standard deviation of the cumulative 131I-­MIBG activity was 20±12 GBq (median, 16 GBq; range, 10–50 GBq). Among the patient groups, no significant absorbed dose difference was found between the submandibular and parotid glands (P>0.24). In comparison to radioiodine therapy, the estimated absorbed dose per activity in MIBG was significantly higher (P<0.001), on average twice as high, contradicting the relationship between the absorbed dose andì clinical observation of glandular side effects.
CONCLUSION: The discrepant salivary gland responses in MIBG and radio iodine therapies suggest a different radiotherapeutical distribution on microscopic scale within the glandular tissue and prove the clinical relevance of a microdosimetric analysis.

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