The Ablation of Thyroid Nodule’s Afferent Arteries Before Radiofrequency Ablation: Preliminary Data

Abstract

Induced radiofrequency thermal ablation is the cytoreductive treatment of symptomatic benign thyroid nodules, metastatic and recurrent thyroid tumors and papillary thyroid microcarcinomas. It is a safe and effective alternative to surgery and it allows to obtain satisfactory results in terms of volumetric reduction of the nodule with significant improvement in the quality of life. The trans-isthmic approach and the moving shot technique are the two basic techniques; however, an advanced technique, artery-first feeding radiofrequency ablation, has been developed and validated. We have prospectively included 29 consecutive patients who have undergone radiofrequency ablation (Group A) or artery- first vRFA (Group B). All included patients had a diagnosis of benign nodular goiter and they underwent a single session of radiofrequency ablation. All patients followed a follow-up program at 1 month, 3 months, and 6 months. Continuous variables (age, TSH value, basal volume of nodule, used Joule, time in second of the procedure, nodules’ volume at 1-, 3-, and 6- months of follow-up and percentage of volume reduction at 1-, 3-, and 6- months of follow-up) were described as mean, standard deviation and range, while categorical variables (gender, nodule structure and nodule vascularization) were described as number of cases and percentage. Independent samples t-test were performed to compare the continuous variables. A Test of Proportions was applied to the categorical variables. The Fisher’s exact test was used to analyze the gender. Statistical significance was considered in case of p-value <0.05. Solid structure and spongiform structure showed statistic differences with p-values of 0.022 and 0.023 respectively between two groups. The percentage of reduction at 1 month did not show a significant difference between two groups; instead, the percentage of volume reduction was decreased mostly in the Group B at 3 months and 6 months of follow-up with a p-value of 0.003 and 0.013, respectively. The Joules/energy used showed a statistically significant difference (p-value=0.05), more energy must be used in vascular radiofrequency ablation. These data allow us to hypothesize that vRFA may improve the effectiveness of the procedure, allowing for a reduction in volume more quickly. They were preliminary but promising results, clearly a larger series of cases and prolonged follow-up are needed to clarify and confirm our observations.

Long-Term Outcomes of Thermal Ablation for Benign Thyroid Nodules: The Issue of Regrowth

“…TA can be used for symptomatic and cosmetic improvement of diffuse and/or multinodular goiter, but these uses have a different context from this review [12,13]. Vascular nodules are resistant to TA because they disperse the input energy [36]. During follow-up, the development of vascularity can lead to regrowth [37].…”

“…During follow-up, the development of vascularity can lead to regrowth [37]. Nodules with a cystic component and spongiform nodules have a tendency to show a greater volume reduction ratio (VRR) over both the short term [36,38] and long term [32].…”

“…Nodule vascularity influences the VRR, regrowth rate, and long-term outcomes [9,15,36]. Blood vessels in nodules disperse the heat generated by ablation devices, creating the so-called heat-sink effect [2].…”

“…During follow-up, if a nodule shows or develops vascularity, it has considerable potential for regrowth [14,43]. Yan et al reported that vascularity was an independent factor associated with regrowth [36], and Wang et al reported that a patient group showing regrowth demonstrated more vascularity than a nonregrowth group [44]. Longitudinal image of the RFA-treated nodule 1 month after the procedure.…”

Current Status and Challenges of US-Guided Radiofrequency Ablation of Thyroid Nodules in the Long Term: A Systematic Review

“…These data suggest that regrowth may be a distinct process from nodule shrinkage, and there might be other factors accounting for it, such as additional patient characteristics (ethnicity and iodine status for instance), as well as the nodule behaviour and/or technical issues. These technical issues include the operator experience, the lack of treatment of the nodule’s margins [ 29 , 48 ] or the lack of treatment of the feeding artery [ 50 ] and the draining vein, the latter of which is usually located at the nodule margins. Also the size and the position of the nodule influence the quality of an RFA treatment, given that the moving-shot technique (i.e., the probe repositioning) is tailored to the patient nodule and in large nodules or nodules whose location is close to critical structures it is difficult to treat the entire nodule [ 47 ].…”