title: Diagnostic accuracy and prognostic value of 18F-FDG PET in Hürthle cell thyroid cancer patients.
abstract: Hürthle cell carcinoma is an uncommon and occasionally aggressive differentiated thyroid cancer associated with increased mortality compared with other differentiated thyroid malignancies. Because it generally has lower iodine avidity, 18F-FDG PET has been suggested as a more accurate imaging modality. However, there is limited information with regard to the true diagnostic accuracy and prognostic value of 18F-FDG PET in this disease.
  
  
  METHODS
  All patients with Hürthle cell thyroid cancer who underwent their first 18F-FDG PET scan between May 1996 and February 2003 were identified retrospectively. 18F-FDG PET scans were reviewed and compared with all available imaging studies, including CT, ultrasound, and radioiodine scintigraphy (RIS). Abnormal 18F-FDG uptake was assessed visually and by measuring the maximum standardized uptake value (SUVmax) of the most intense lesion. Clinical follow-up for at least 1 y or until death was required for inclusion.
  
  
  RESULTS
  Forty-four patients met inclusion criteria. The median follow-up was 2.9 y. There were 24 positive and 20 negative 18F-FDG PET scans with 1 false-positive and 1 false-negative study, resulting in a diagnostic sensitivity of 95.8% and a specificity of 95%. In 5 of 11 patients who had both positive CT and 18F-FDG PET findings, 18F-FDG PET revealed additional sites of disease. Furthermore, 18F-FDG PET correctly classified as negative 3 patients with false-positive CT findings. In 3 of 6 patients with positive RIS, 18F-FDG PET revealed additional sites of metastatic disease. Ten patients with positive 18F-FDG PET had negative RIS. Only 1 patient with negative 18F-FDG PET had positive RIS. The SUVmax also provided prognostic information: In a stepwise fashion, each increase in intensity by SUVmax unit was associated with a 6% increase in mortality (P < 0.001). The 5-y overall survival in patients with SUVmax < 10 was 92%; it declined to 64% in those with SUVmax > 10 (P < 0.01).
  
  
  CONCLUSIONS
  18F-FDG PET has excellent diagnostic accuracy in Hürthle cell thyroid cancer patients, improving on CT and RIS. Intense 18F-FDG uptake in lesions is an indicator of a poor prognosis. Our data suggest that all patients with Hürthle cell thyroid cancer should undergo 18F-FDG PET as part of their initial postoperative staging and periodically to screen for occult recurrence, particularly in patients with elevated serum thyroglobulin.
authors.affiliation: Nuclear Medicine Service, Memorial Sloan-Kettering Cancer Center, New York, New York, USA. prymada@upmc.edu
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Pryma
authors.forename: Heiko
authors.initials: H
authors.lastname: Schöder
authors.forename: Mithat
authors.initials: M
authors.lastname: Gönen
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Robbins
authors.forename: Steven M
authors.initials: SM
authors.lastname: Larson
authors.forename: Henry W D
authors.initials: HW
authors.lastname: Yeung
mesh_terms: D018249:Adenoma, Oxyphilic / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011379:Prognosis; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin