The Prognostic Values of Preoperative Tumor Volume and Tumor Diameter in T1N0 Papillary Thyroid Cancer

PURPOSE The current TNM staging system for papillary thyroid cancer (PTC), which is based on tumor diameter, may not precisely reflect the true tumor burden. Therefore, we investigated whether preoperative tumor volume might more accurately reflect tumor burden and predict prognosis in patients with T1N0 PTC than preoperative tumor diameter. MATERIALS AND METHODS We retrospectively reviewed data from 1,659 patients with T1N0 PTC, and after exclusion, a total of 1,081 patients were ultimately included. Tumor volume (V) was calculated for all patients using preoperative ultrasonography, and patients were grouped according to tumor diameter (T1a vs. T1b) and tumor volume (V1a vs. V1b). The recurrence-free survival (RFS) rates were then compared for these groups. RESULTS The mean follow-up time was 66.12±28.75 months, and 97.2% of the cohort experienced RFS. The optimal volume cut-off was defined as 0.545 cm3. There were no differences in RFS rates between T1a/T1b groups (all ages) and V1a/V1b groups (< 45 years of age). However, ≥ 45-year-old patients in the V1b group had a significantly poorer RFS rate than those in the V1a group. These results were confirmed by multivariate analysis. CONCLUSION Our results indicate that preoperative tumor volume may be more useful for predicting prognosis than tumor diameter in ≥ 45-year-old patients with T1N0 PTC.