Initial ablation ratio predicting the recurrence of low-risk papillary thyroid microcarcinomas treated with microwave ablation: a 5-year, single-institution cohort study.

The mean tumor volume of PTMC before MWA was 0.071 (0.039, 0.121) cm3, with a maximum diameter of 0.60±0.18 cm. All PTMC patients were followed up for 6 (3, 18) months. Va increased immediately after MWA, then gradually decreased over time, till significantly smaller at 12 months than that before MWA (P<0.05). The median volume reduction ratio (VRR) at 24 months reached 100%, which was maintained during a 60-month follow-up. A total of 7 (4.55%) cases of local tumor progression were recorded during the follow-up. Kaplan-Meier survival analysis revealed that the rate of local tumor progression was significantly lower in PTMC patients with a maximum tumor diameter <0.70 cm than in those with ≥0.70 cm (P=0.031). A significant better prognosis was achieved in PTMC patients with IAR≥15 than in those with IAR<15 (P=0.015). Sex, age (<55 years) and preoperative thyroid-stimulating hormone (TSH>2.0 mU/L) of PTMC patients were not correlated with local tumor progression.