18F-FDG PET reduces unnecessary hemithyroidectomies for thyroid nodules with inconclusive cytologic results.

UNLABELLED: Fine-needle aspiration biopsy (FNAB) is inconclusive in up to 20% of patients with solitary thyroid nodules. In these cases, hemithyroidectomy is necessary, but only 20% of the nodules prove to be thyroid carcinoma. The aim of this study was to explore the potential of (18)F-FDG PET to reduce the number of unnecessary hemithyroidectomies in the preoperative assessment of thyroid nodules with inconclusive FNAB results.

METHODS: Forty-four consecutive patients, scheduled for hemithyroidectomy because of inconclusive FNAB findings, participated in this prospective study. (18)F-FDG PET of the thyroid region was performed before hemithyroidectomy, and standardized uptake values were calculated. The final histopathologic diagnosis served as a standard of reference.

RESULTS: Histopathologic examination of the surgical specimens revealed 7 well-differentiated thyroid carcinomas in 6 patients, all accumulating (18)F-FDG (negative predictive value, 100%). (18)F-FDG accumulated in 13 of 38 benign nodules. The pre-PET probability for cancer in this study population was 14% (6/44), and the post-PET probability increased to 32% (6/19). The percentage of unnecessary hemithyroidectomies in a hypothetical algorithm using (18)F-FDG PET was only 30% (13/44), compared with 86% (38/44) without (18)F-FDG PET. (18)F-FDG PET reduced the number of futile hemithyroidectomies by 66% (25/38) (95% confidence interval, 49%-80%; Fisher's exact test, P = 0.0038). Semiquantitative analysis using standardized uptake values did not help to further reduce this number.

CONCLUSION: In addition to data in the literature demonstrating accurate detection of thyroid cancer by (18)F-FDG PET, this study showed that (18)F-FDG PET should play an important role in the management of patients with inconclusive cytologic diagnosis of a thyroid nodule. (18)F-FDG PET reduced the number of futile hemithyroidectomies by 66%. Although PET is a relatively costly procedure, this cost outweighs the costs and risks associated with unnecessary thyroid surgery.