Preoperative diagnostic value [F-18] fluorodeoxyglucose positron emission tomography in patients with radioiodine-negative recurrent well-differentiated thyroid carcinoma

Objective To assess the utility of 2-[F-18] fluoro-2-deoxy-D-glucose positr on emission tomography (FDG-PET) to detect recurrent disease in the follow- up of patients with well-differentiated thyroid cancer (WDTC) who have nega tive diagnostic I-131 scans and abnormal thyroglobulin levels. Summary Background Data In general, patients with WDTC have an excellent lo ng-term prognosis when appropriate surgical treatment and follow-up are car ded out. After total thyroid ablation, whole-body I-131 scintigraphy and me asurement of serum thyroglobulin are useful diagnostic tools to detect pers istent or recurrent malignancy. In case of tumor dedifferentiation, decreas ed or lost iodine-accumulating ability may lead to false-negative I-131 sca nning results. The diagnostic and therapeutic delay is responsible for a po or prognosis in this subgroup of patients. Efforts have been made in the se arch for suitable imaging modalities capable of early detection of recurren t thyroid carcinoma. Methods The authors prospectively analyzed 24 patients with WDTC, negative results of whole-body I-131 scintigraphy, and elevated serum thyroglobulin concentrations. Attenuation-corrected whole-body FDG-PET scans from the nec k to the upper legs were performed. In addition, all patients underwent cer vical ultrasonography, The results of the imaging studies were compared wit h histopathologic findings. If no resection of the suspicious lesion was ca rried out, computed tomography data were used as control criteria. Results Overall, FDG-PET disclosed 38 hot spots. The sensitivity of the met hod was 94.6%, but the specificity was lower (25.0%). The diagnostic accura cy was 87.8%. There were three false-positive results in two patients with benign cervical lymph nodes. In one patient with regional lymph node metast ases in the neck, two false-negative results were obtained. Ultrasound clas sified both findings as malignant, however. Because of unexpected findings, FDG-PET suggested potential modification of the surgical management in nin e patients. Distant metastases could be disclosed using FDG-PET in only thr ee patients. Conclusions FDG-PET is a useful diagnostic tool in the follow-up of thyroid ectomized patients with WDTC, negative I-131 scanning results, and abnormal serum thyroglobulin concentrations, The method detects metastatic disease in 94.6% of cases. PET results changed surgical tactics in a significant nu mber of patients. Accurate staging of locoregional cancer recurrence in the neck may be consummately obtained by concomitant analysis of PET and ultra sound results.