Risk factors and stratification for recurrence of patients with differentiated thyroid cancer, elevated thyroglobulin and negative I-131 whole-body scan, by restaging18F-FDG PET/CT.
OBJECTIVE
In nearly 20%-30% of patients with differentiated thyroid carcinoma (DTC) relapse and 7% of them die during the next 10 years after initial diagnosis. In 10%-30% of patients with DTC after ablation therapy during the follow-up show a negative iodine-131 (131I) whole-body screening test (131I WBS) and increased serum thyroglobulin (Tg) level. Loss of ability of DTC metastatic lesions to trap131I is associated with pure survival and often aggressive disease. Several studies have shown that in DTC cases non trapping131I, fluorine-18-fluorodeoxyglucose positron emission tomography (18F-FDG PET) can detect recurrence or metastases with high sensitivity (80%-90%). The purpose of this study was to investigate the clinicopathologic features and other related risk factors of patients with DTC having elevated Tg levels and negative131I WBS in which recurrence was detected by18F-FDG PET/CT. We tried to study and stratify patients in this grey zone who could benefit from18F-FDG PET/CT for the detection of metastases/recurrence according to predefined risk factors not investigated by other researchers.


METHODS
We studied retrospectively 165 DTC patients with elevated Tg levels and a negative131I WBS during their follow-up between 2004-2015. Metastases/recurrence was found in 49% of the patients on restaging with18F-FDG PET/CT and were compared with nonmetastatic group according to predefined risk factors. These factors were also evaluated in true positive and false negative cases.


RESULTS
The sensitivity and specificity of18F-FDG PET/CT for detecting recurrent/metastatic disease were 90% and 98.5%, respectively. No apparent predefined risk factor impacting a false negative18F-FDG PET/CT was found. Findings in follicular carcinoma, Hürtle cell carcinoma and papillary carcinoma were not different from positive PET findings. The variants of papillary carcinoma also had no statistically difference with regard to18F-FDG results.


CONCLUSIONS
The most important factors affecting a true positive18F-FDG PET/CT study were: ETE, high total131I dose and the SUVmax values over 4.5.
Department of Nuclear Medicine, Gulhane Military Medical Academy and Medical Faculty, 06018, Ankara, Turkey. since@gata.edu.tr.
Kursat
K
Okuyucu
Semra
S
Ince
Engin
E
Alagoz
Ozdes
O
Emer
Huseyin
H
San
Elif
E
Balkan
Aslı
A
Ayan
Coskun
C
Meric
Cem
C
Haymana
Cengizhan
C
Acıkel
Bengul
B
Gunalp
Alper Ozgur
AO
Karacalioglu
Nuri
N
Arslan
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000453:epidemiology* / Q000473:pathology*; D009367:Neoplasm Staging; D000072078:Positron Emission Tomography Computed Tomography / Q000706:statistics & numerical data*; D015995:Prevalence; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000453:epidemiology* / Q000473:pathology*; D014421:Turkey / Q000453:epidemiology; D051598:Whole Body Imaging / Q000706:statistics & numerical data; D055815:Young Adult
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin