Twelve-Month Volume Reduction Ratio Predicts Regrowth and Time to Regrowth in Thyroid Nodules Submitted to Laser Ablation: A 5-Year Follow-Up Retrospective Study

Abstract

Objective: Laser ablation is a therapeutic modality used to reduce the volume of large benign thyroid nodules. Unsatisfactory reduction and regrowth are observed in some treated nodules. The aim of the study was to evaluate the long-term outcomes of laser treatment for solid nodules during a 5-year follow-up period, the regrowth rate, and the predictive risk factors of nodule regrowth. Materials and Methods: We retrospectively evaluated patients with benign, solid, cold thyroid nodules who underwent laser ablation and were followed-up for 5 years. According to the selection criteria, 104 patients were included (median baseline nodule volume, 12.5 mL [25.0-75.0%, 8-18 mL]; median energy delivered, 481.5 J/mL [25.0-75.0%, 370-620 J/mL]). Nodule volume, thyroid function test results, and ultrasound were evaluated at baseline and then annually after the procedure. Results: Of 104 patients, 31 patients (29.8%) had a 12-month volume reduction ratio (VRR) < 50.0% and 39 (37.5%) experienced nodule regrowth. Of these 39 patients, 17 (43.6%) underwent surgery and 14 (35.9%) underwent a second laser treatment. The rate of nodule regrowth was inversely related to the 12-month VRR, i.e., the lower the 12-month VRR, the higher the risk of regrowth (p < 0.001). The mean time for nodule regrowth was 33.5 ± 16.6 months. The 12-month VRR was directly related to time to regrowth, i.e., the lower the 12-month VRR, the shorter the time to regrowth (p < 0.001; R 2 = 0.3516). Non-spongiform composition increased the risk of regrowth with an odds ratio of 4.3 (95% confidence interval [CI] 1.8-10.2; p < 0.001); 12-month VRR < 50.0% increased the risk of regrowth with an odds ratio of 11.7 (95% CI 4.2-32.2; p < 0.001). Conclusion: The VRR of thyroid nodules subjected to similar amounts of laser energy varies widely and depends on the nodule composition; non-spongiform nodules are reduced to a lesser extent and regrow more frequently than spongiform nodules. A 12-month VRR < 50.0% is a predictive risk factor for regrowth and correlates with the time to regrowth.

Residual vital ratio: predicting regrowth after radiofrequency ablation for benign thyroid nodules

“…As alternatives to surgery, the long-term efficacy of thermal ablation techniques has attracted research attention. Sim et al [20] found that the nodule regrowth began at 12 months and tended to be prominent after 2 years of follow-up with an incidence of 4.1-37.5% [19][20][21][22][23][24]. Recently, a multicenter study found that regrowth occurred in 20% of patients who were followed for 5 years after a single session of RFA [25].…”

“…Second, the sample size was relatively small, partially in the regrowth group, resulting in a small number for events per variable in logistic regression analysis. However, the overall incidence of nodule regrowth was only 4.1 to 37.5% [19][20][21][22][23][24][25]. It was very difficult to collect enough data for events per variable.…”

“…A meta-analysis showed that the volume reduction rate(VRR) at 6, 12 and 24 months after RFA was 68%, 75% and 87%, respectively [8]. However, some studies reported that 4.1-37.5% of the treated nodule occurred regrowth after 2 to 3 years of ablation [19][20][21][22][23][24][25]. Regrowth was defined as an increase in nodule volume 50% over the previously recorded smallest volume [26], which was usually observed at the untreated peripheral area and needed additional treatment [19][20][21][22][23].…”

Letter to the editor regarding residual vital ratio: predicting regrowth after radiofrequency ablation for benign thyroid nodules

“…There have been similar studies previously. In a study by Negro et al who retrospectively analyzed the results of 5-year follow-up after laser ablation, a 12-month VRR < 50.0% is a predictive risk factor for regrowth and correlates with the time to regrowth [5]. In addition, Sim and Park observed that the IAR is linearly correlated with the 12month VRR, and if IAR < 70%, it can be used for the early prediction of regrowth [6,7].…”

Letter: Twelve-Month Volume Reduction Ratio Predicts Regrowth and Time to Regrowth in Thyroid Nodules Submitted to Laser Ablation: A 5-Year Follow-Up Retrospective Study

“…Dear Editor, I read with great interest the report by Negro et al (1) titled "Twelve-Month Volume Reduction Ratio Predicts Regrowth and Time to Regrowth in Thyroid Nodules Submitted to Laser Ablation: A 5-Year Follow-Up Retrospective Study." This study presented long-term follow-up results of single session laser ablation (LA) for symptomatic benign thyroid nodules.…”