FDG PET/CT in differentiated thyroid cancer patients with low thyroglobulin levels

Abstract

Objective To evaluate usefulness of [18F]fluorodeoxyglucose (FDG) PET/CT in patients with low detectable thyroglobulin levels suspicious for persistent or recurrent differentiated thyroid cancer (DTC). Methods A retrospective case series study evaluating FDG PET/CT in patients with detectable thyroglobulin (Tg) levels (≥ 0.20 ng/mL and <10.00 ng/mL) after initial treatment with total thyroidectomy and I-131 thyroid remnant ablation for pT1-3aN0-1bM0 DTC. Sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of FDG PET/CT were calculated. Results Twenty-seven patients underwent FDG PET/CT. Median Tg level at FDG PET/CT was 2.00 ng/ml (range 0.30-9.00). FDG PET/CT was positive in 14 patients (51.9%): lesions suspicious for lymph node metastases were depicted in 12 patients, and lung metastases in 2. DTC was confirmed in 13/14 FDG PET/CT positive patients. In 9/13 patients with a negative FDG PET/CT DTC was confirmed ≤3 months after FDG PET/CT. The sensitivity, PPV, specificity and NPV were: 59.1%, 92.9%, 80.0% and 30.8%, respectively. Conclusions This case series shows that FDG PET/CT might be useful to detect persistent or recurrent DTC in patients with low detectable Tg. However, when FDG PET/CT is negative, this does not rule out DTC and further investigations are necessary.

I‐PET score: Combining whole body iodine and 18F‐FDG PET/CT imaging to predict progression in structurally or biochemically incomplete thyroid cancer

“…FDG PET imaging has become increasingly important in management of patients with thyroid cancer, with FDG avid disease associated with poor prognosis 16–22 . FDG PET imaging have a role in detecting recurrence or persistent disease in both patients with negative WBS and elevated Tg (>10 ng/ml), and those with Tg < 10 ng/ml after initial treatment 21,23–26 . The degree of FDG avidity has been associated with poor survival 5,17,25,27,28 and associated with poor response to RAI 29 .…”

“…[16][17][18][19][20][21][22] FDG PET imaging have a role in detecting recurrence or persistent disease in both patients with negative WBS and elevated Tg (>10 ng/ml), and those with Tg < 10 ng/ml after initial treatment. 21,[23][24][25][26] The degree of FDG avidity has been associated with poor survival 5,17,25,27,28 and associated with poor response to RAI. 29 In our cohort, I-PET [3] identified patients who had become refractory to RAI with high rates of progression; these patients were more likely to receive a mutlikinase inhibitor and were at increased risk of death from their disease.…”

The potential role of reprogrammed glucose metabolism: an emerging actionable codependent target in thyroid cancer

“…However, 18F-FDG PET/CT is strongly recommended for follow-up of high-risk patients with elevated serum thyroglobulin (Tg) and negative 131I imaging [ 164 , 165 ]. FDG PET has been shown to be helpful in detecting persistent or recurrent DTC in patients with low Tg; however, when FDG PET-CT is negative, this does not exclude DTC and requires further investigation [ 166 ].…”