Shinji Ito, Presenter: Nothing to Disclose

Shingo Iwano MD, Abstract Co-Author: Nothing to Disclose

Katsuhiko Kato MD,PhD, Abstract Co-Author: Nothing to Disclose

Shinji Naganawa MD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to evaluate the efficacy of I-131 therapy for bone metastases of differentiated thyroid carcinoma (DTC) by F-18 FDG-PET/CT.

We evaluated 41 bone metastases of 12 patients (2 male, 10 females; age 33 to 70y: mean age 59±10y) with DTC. F-18 FDG-PET/CT scan was performed before and 6 months after the I-131 therapy. We measured the size and the maximum standardized uptake value (SUVmax) of the bone metastases before and after the therapy, and compared these values before and after the therapy. The uptake of I-131 for lesions were also checked 7 days after the therapy.

After the therapy, the size of metastatic lesions was decreased in 17 lesions, increased in 11 lesions, and did not change in 10 lesions, whereas SUVmax was decreased in 36 of 41 lesions and increased in 5 lesions after the therapy. The mean size of lesions before and after the therapy was 24.0mm and 23.5mm, respectively, and the difference between these values was not statistically significant (p = 0.15). The mean ratio of size of lesions before and after the treatment was 1.00. However, the mean SUVmax of lesions was significantly decreased from 4.4 to 3.6 (p < 0.005), and the mean ratio of SUVmax before and after the therapy was 0.82. Serum thyrogloblin was also checked before and after the therapy and was found to decline in 10 patients and elevate in 2 patients. In one of the latter cases, there was a lesion having an increased SUVmax from 6.3 to 13.8. After the therapy, I-131 did not accumulate in 2 lesions of 2 patients, and the uptake of FDG increased in one of the 2 lesions.

This study suggested that F-18 FDG-PET/CT is a promising tool to evaluate I-131 therapy for bone metastases of DTC.

F-18 FDG-PET/CT can assess the reponse of I-131 therapy for bone metastases of DTC.

Ito, S, Iwano, S, Kato, K, Naganawa, S, F-18 FDG-PET/CT for Evaluation of I-131 Radioiodine Therapy for Bone Metastases of Differentiated Thyroid Carcinoma.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12027437.html