J Nucl Med 2001 Oct;42(10):1464-9
Clinical impact of (18)F-FDG PET in thyroid carcinoma patients with elevated
thyroglobulin levels and negative (131)I scanning results after therapy.
Helal BO, Merlet P, Toubert ME, Franc B, Schvartz C, Gauthier-Koelesnikov H,
Prigent A, Syrota A.
18F-FDG PET has been shown to effectively detect differentiated thyroid
carcinoma (DTC) metastases with impaired iodine-trapping ability. This article
evaluates the potential contribution of FDG PET in the follow-up of patients
with differentiated thyroid carcinoma, elevated thyroglobulin (Tg) levels, and
negative whole-body scan results obtained after high doses of (131)I. METHODS:
We prospectively assessed the ability of FDG to detect metastases in 37 DTC
patients who had undergone total thyroidectomy and radioactive ablation and
presented with persistent disease, as assessed from elevated Tg levels and
negative results of whole-body scans performed after therapeutic doses of
(131)I. Additional conventional imaging procedures were performed to detect
residual disease, and the patients were divided into 2 groups: group 1, with
positive conventional imaging findings (n = 10), and group 2, with negative
conventional imaging findings (n = 27). RESULTS: FDG PET showed positive
findings in 28 patients and accurately localized tumor sites in 89% of them. In
group 1, FDG PET confirmed 17 of 18 previously known tumor sites and detected 11
additional sites. In group 2, FDG PET findings were positive in 19 of 27
patients with no previously detected metastases. PET was effective for both low-
and high-stage tumors. The FDG data led to a change in the clinical management
of 29 of 37 patients with further surgical resection in 23 patients, 14 of whom
achieved disease-free status, and external radiation therapy in 4 patients.
CONCLUSION: FDG PET is able to detect metastases undetected by (131)I
posttherapy whole-body scanning in patients with elevated Tg levels. It should
be proposed as a first-line investigation in patients with persistent disease
but negative findings on (131)I whole-body scans after treatment.
