Preoperative fluorodeoxyglucose positron emission tomography-computed tomography in papillary thyroid cancer: A futile exercise

Dear Sir,

I read with great interest the article by Kim et al., ¹ which describes a study undertaken in a high-volume centre where 194 thyroid surgery procedures were performed in a 1-year period. The role of fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) in papillary thyroid cancer (PTC) may be seen in two clinical scenarios: first as an initial preoperative imaging technique; secondly as a part of follow-up imaging. Negative whole-body radioiodine scanning, with elevated thyroglobulin levels, in the follow up of patients with PTC has largely been accepted as an indication for FDG PET-CT.^2–4

Kim et al. ¹ addressed a pertinent issue of FDG PET-CT as an initial preoperative investigation in PTC. They reported the sensitivity of FDG PET-CT in detecting central and lateral lymph node metastases as being 4.3% (3/70) and 62.5% (15/24), respectively. The dismal sensitivity in detecting central lymph node metastasis seems likely to be due to the masking effect of primary thyroid lesion uptake of FDG. The reporting of the specificity, positive predictive and negative predictive value of FDG PET-CT in central and lateral lymph node metastasis in the article would have given a fuller picture to help understand the utility of FDG PET-CT. In addition, a brief mention of distant metastasis, if detected in any of these patients, would have been an interesting fact to be noted in the Kim study. ¹ Choi et al. ⁵ also evaluated the role of preoperative FDG PET-CT and compared this technique with ultrasonography for the detection of cervical lymph node metastasis: their paper was a prospective study involving 65 patients with PTC. Choi et al. also reported poor sensitivity and positive predictive value of FDG PET-CT in detecting such metastases, and concluded that FDG PET-CT did not confer any added advantage over neck ultrasonography in the initial staging of PTC. ⁵ So, it can be concluded from these reports that current literature does not support preoperative FDG PET-CT in the initial staging of PTC.