There are various minimally invasive treatments for benign thyroid nodules, including percutaneous ethanol injection (PEI), radiofrequency, and laser ablation. The former was first performed in 1990 for autonomously functioning thyroid nodules, and it leads to coagulative necrosis and small vessels thrombosis followed by inflammatory changes, consequently result in fibrosis, shrinkage, and volume reduction of the treated zone [16–20].
PEI is the first-line treatment for the relapsing thyroid cyst, and it doesn't need local anesthesia. Significant complications are rare. However, some cases of vocal cord paresis have been reported due to the injection of ethanol outside the cystic cavity. In hyperfunction nodules, the PEI is reported to be associated with a remained risk of hyperthyroidism relapse and progressive regrowth in 70% of patients. Also, the use of PEI in solid thyroid nodules is contraindicated, unless it is the only available treatment [20–24]. According to the studies, PEI in nonfunctioning nodules had been associated with about 50% of nodular volume reduction [25–27]. Consistent with previous studies, in our research, the PEI was associated with the mean volume reduction of 37.4%, 55.6%, and 72.2%, at the baseline of the study, 1, 3 and six months after the intervention, respectively.
The radiofrequency ablation (RFA) was first performed in2005, and it induces thermal damage followed by coagulative necrosis in the treated zone, leading to nodule shrinkage and fibrosis. Radiofrequency ablation is usually performed under local anesthesia. perithyroidal hemorrhage, recurrent nerve damage, nodule rupture, and skin burns are some of the common consequences which have been reported secondary to the radiofrequency ablation [20, 28]. However, the complication rate is low, and it is reported only in 3.3%of patients [29, 30]. Also, according to the scholars, most of these complications are reversible and go away in long-term follow-ups. According to the studies, radiofrequency ablation has been reported to decrease nodule size by about 50% after six months and by nearly 80%, one year after the intervention[29, 31, 32]. Similar to the previous studies, in our research, in radiofrequency ablation group, the mean volume reduction at the baseline of the study, 1, 3 and six months after the intervention were 46.4%, 64.2%, and 83.4%, respectively. It is should also be noted that during the follow-up no complication was observed among our patients.
In a study by Mauri et al., they indicated that percutaneous laser ablation (PLA) and RFA are similarly effective for the treatment of benign thyroid nodules with similar outcome in volume reduction at 1, 6 and 12 months and with the same rate of complications [32].
In a study by Ha et al., they conducted a meta-analysis comparing RFA and PLA for the treatment of thyroid nodules, and they found a 77.8% of mean volume reduction at 6 months in RFA treated group compared with 49.5% in PLA treated group, claiming that RFA seems to be better than PLA in decreasing benign solid thyroid nodule volume [33].
In a randomized trial conducted by Noe Bennedbæk et al., they investigated the effect of percutaneous ethanol injection therapy versus L-thyroxine medical treatment on benign solitary solid cold thyroid nodules, and they concluded that PEI as a single small dose of ethanol is superior to l-T4suppressive therapy, but is still inferior to surgery [34].
In a prospective randomized study conducted by Yin Huh et al., they investigated the efficacy of additional radiofrequency ablation treatment sessions on symptomatic benign thyroid nodules, and they concluded that a single-session of RF ablation is effective in most patients for improving their cosmetic and symptomatic problems by reducing nodule volume [35].
In a prospective semi-experimental study conducted by Yong Sung et al., on the single-session treatment of benign cystic thyroid nodules with ethanol versus radiofrequency ablation they concluded that both ethanol injection (EA) and RF ablation were helpful and safe treatment modalities, the mean volume reduction of the EA group was non-inferior to and also meaningfully superior to that of the RF ablation group. Therefore, EA could be the leading treatment modality for cystic thyroid nodules, which has equivalent therapeutic efficacy but is more cost-benefit than RF ablation [36].
Our study showed that there is no significant relationship between age, gender, and BMI and mean volume reduction in 1, 3, and six months after the intervention.