The management of papillary thyroid carcinoma (PTC) should be decided by Risk-adapted approach. However, intermediated risk PTC needs to be stratified more precisely. Otherwise, the utility of 18F-FDG PET images in patients with PTC is restrictive. The aim of this study was to investigate the prognostic value of Metabolic Tumor Volume (MTV) measured on 18F-FDG PET images in patients with papillary thyroid carcinoma treated with surgery.
We retrospectively analyzed 102 patients with PTC who underwent 18F-FDG PET/CT between Feburary 2009 and June 2017 at Osaka University Medical School Hospital for initial staging before surgery. We evaluated the association of MTV of primary tumor (T-MTV) with relapse-free survival (RFS) using Cox regression analysis. Receiver operating characteristic (ROC) curves were used to estimate the optimal cut-off values for T-MTV. We also conducted recursive partitioning analyses to offer a novel risk stratification system.
The 3-year RFS for all patients were 81.2% with median follow-up of 42 months (range 11-111). In Cox model, T-MTV (Hazard Ratio, 1.23; 95% CI, 1.08 to 1.38; P = 0.002) was significantly associated with RFS. ROC analyses showed that the optimal cutoff value of T-MTV was 10.3ml. We classified the patients as having a low, intermediate, or high risk of relapse or death on the basis of T-MTV and lymph node metastasis.
MTV of primary tumor was a significant prognostic factor for RFS in patients with PTC treated with surgery. Incorporation of T-MTV into staging may lead to a better risk stratification.
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All authors have declared no conflicts of interest.