FDG-PET performed concurrently with initial I-131 ablation for differentiated thyroid cancer.

Abstract

OBJECTIVE:

Differentiated thyroid cancers (DTCs) are commonly treated by total thyroidectomy followed by I-131 radioiodine ablation to eradicate any residual thyroid tissue and to detect any metastatic lesions on post-treatment whole body scans (TxWBS). However, some DTCs do not trap iodine, resulting in negative whole body scanning. Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) has proven to be a valuable diagnostic technique for detecting many types of malignant tumors and metastases. The purpose of this study was to evaluate FDG-PET performed concurrently with initial I-131 ablation for its ability to detect lymph node metastasis and for its role in the management of DTC patients.

METHODS:

A total of 54 patients (16 males and 38 females; median age = 50 years) with histologically proven DTC underwent both FDG-PET and subsequent I-131 ablation. A dose of 3.7 GBq I-131 was administered to 51 patients, 2.96 GBq was administered to 1 patient, and 2.22 GBq was administered to 2 patients. FDG-PET or PET/CT was performed 3-4 days prior to ablation. TxWBS was conducted 1 week after therapy. FDG-PET scans and TxWBS were interpreted by consensus of 2 experienced radiologists. Serum thyroglobulin (Tg) levels at 3-6 months after ablation were compared between PET-positive and PET-negative patients.

RESULTS:

FDG-PET was positive in 25 sites (thyroid bed: n = 9; cervical lymph nodes: n = 12; mediastinal lymph nodes: n = 3; and axillary lymph nodes: n = 1) of 18 patients (33%). Only 5 of 16 lymph nodes (31%) that were PET-positive were also positive on TxWBS. The success rate of Tg-negative after ablation was significantly lower for patients with PET-positive scans than for those with PET-negative scans (p = 0.026).

CONCLUSIONS:

FDG-PET performed concurrently with I-131 ablation can detect lymph node metastases in which radioiodine does not accumulate and may influence the management and treatment options for DTC patients.

• Authors: Shingo Iwano, Katsuhiko Kato, Shinji Ito, Kenichi Tsuchiya, Shinji Naganawa
• Journal: Annals of nuclear medicine (Ann Nucl Med) Vol. 26 Issue 3 Pg. 207-13 (Apr 2012) ISSN: 1864-6433 [Electronic] Japan
• PMID: 22160654 (Publication Type: Journal Article)

Chemical References

• Iodine Radioisotopes
• Fluorodeoxyglucose F18
• Thyroglobulin

Topics

• Ablation Techniques
• Adolescent
• Adult
• Aged
• Female
• Fluorodeoxyglucose F18
• Humans
• Iodine Radioisotopes (therapeutic use)
• Lymphatic Metastasis
• Male
• Middle Aged
• Multimodal Imaging
• Positron-Emission Tomography (methods)
• Retrospective Studies
• Thyroglobulin (blood)
• Thyroid Neoplasms (blood, diagnostic imaging, pathology, surgery)
• Time Factors
• Tomography, X-Ray Computed
• Whole Body Imaging
• Young Adult