Shigeki Nagamachi MD, PhD, Presenter: Nothing to Disclose

Hideyuki Wakamatsu MD, Abstract Co-Author: Nothing to Disclose

Seigo Fujita, Abstract Co-Author: Nothing to Disclose

Shozo Tamura MD, PhD, Abstract Co-Author: Nothing to Disclose

Masaomi Kuroki MD, Abstract Co-Author: Nothing to Disclose

Hiroshi Nakada MD, Abstract Co-Author: Nothing to Disclose

Ryuichi Nishii MD, Abstract Co-Author: Nothing to Disclose

Kiyohisa Kamimura MD, Abstract Co-Author: Nothing to Disclose

Kiyoshi Nishikawa, Abstract Co-Author: Nothing to Disclose

Shogo Kiyohara, Abstract Co-Author: Nothing to Disclose

Hideo Arita PhD, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

Few studies have compared FDG PET/CT with I-131　whole body scintigraphy (IWBS), chest diffusion weighted imaging (DWI). The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from IWBS and chest DWI. We also clarify association between short-term prognosis and scintigraphic pattern

Whole-body FDG PET/CT was performed on 53 patients (20 men, 33 women;32-78yr; mean age, 56 y) with differentiated thyroid cancer (5 cases of follicular cancer and 48 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including thyroglobulin (Tg ) level and histopathological findings to allow a comparison with imaging results. In the lesion base analysis, metastatic organs were divided into three areas: lymph nodes, lung and bone. For analyzing association with scintigraphic pattern and predicting therapeutic effect, we divided all cases into two groups based on the superiority of uptake on the whole body imaging, namely the higher FDG uptake group (F group) and the higher accumulation of I-131 group (I group). Six months after I-131 therapy, therapeutic effect (good or poor) was determined based on the Tg levels.

The number of lesions detected by all scintigraphic methods totaled 68. The positive rate of each modality was 43 (63.2%) by FDG-PET alone, 64 (94.1%) by FDG-PET/CT, 50 (73.5%) by IWBS and 38 (55.9%) by DWI respectively. FDG uptake was concordant with IWBS in only 26 lesions (38.2%). FDG uptake was concordant with DWI uptake in 36 lesions (52.9%). Using both PET/CT and IWBS, all lesions were detected. In the relationship with therapeutic effect, F group tended to be poor prognosis compared with I group.

FDG PET/CT and IWBS provide complementary information in diagnosing post-operative thyroid cancer metastasis, whereas FDG PET/CT provides results similar to those of DWI. Thus, the combination of IWBS and FDG PET/CT (or DWI) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy. Based on the result that F group tended to show poor prognosis compared with I group, we may also predict short-term prognosis by the pattern of tracer distribution.

FDG PET/CT and IWBS are complimentary useful for both detection and predict prognosis in post-operative thyroid cancer metastasis

Nagamachi, S, Wakamatsu, H, Fujita, S, Tamura, S, Kuroki, M, Nakada, H, Nishii, R, Kamimura, K, Nishikawa, K, Kiyohara, S, Arita, H, et al, , Comparison of Diagnostic Performance between FDG-PET/CT, I-131 Scintigraphy and Diffusion-weighted MR in Postoperative Thyroid Cancer Metastasis: Detectability and Prognostic Capability.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6015313.html