Identifying predictive factors for efficacy in high intensity focused ultrasound (HIFU) ablation of benign thyroid nodules - a retrospective analysis

Objective: Since it is unclear whether clinical parameters can independently predict the subsequent treatment response following high intensity focused ultrasound (HIFU) ablation of benign thyroid nodules, we aimed to examine clinical factors that may independently predict 12-month efficacy after HIFU treatment.Methods: One hundred and forty patients who had single ablation were categorized into two groups, those with 12-month nodule shrinkage above the median (Group I, n = 70) and with shrinkage below or equal to the median (Group II, n = 70). Baseline characteristics, treatment parameters, percentage change in serum TSH, Free thyroxine (FT4) and thyroglobulin (Tg) from baseline to Day 4 and appearance of microbubbles (hyperechoic marks (HEMs)) during treatment were compared between groups. To determine independent factors, a multivariate analysis was done by logistic regression analysis.Results: Baseline characteristics and treatment parameters were comparable between groups. However, on Day-4, group I had significantly lower serum TSH (0.49mIU/L vs. 0.84mIU/L, p = 0.011) and higher FT4 (22.11 pmol/L vs. 18.47 pmol/L, p = 0.008) than group II. The percentage change in TSH, FT4 and Tg were significantly greater in group I (p = 0.002, p = 0.009 and p = 0.001 respectively). The proportion of HEMs observed during treatment was also significantly higher in group I (42.69% vs. 31.72%, p = 0.030). Among the significant factors, the percentage change in FT4 was the only independent factor for 12-month shrinkage (OR = 1.018, 95%CI =1.003-1.032, p = 0.017).Conclusions: Percentage change in serum FT4 on post-treatment Day-4 was an independent blood parameter for the subsequent nodule shrinkage at 12 months. This finding could potentially facilitate the decision for earlier retreatment of treated nodules.