Thermal ablation techniques, including radiofrequency, laser, and microwave ablation, are relatively safe and effective for the treatment of papillary thyroid microcarcinoma (PTMC), according to study results published in Thyroid.

The prognosis of PTMC, defined as a <1.0-cm papillary thyroid carcinoma, is favorable, and although surgery is the first-line treatment, it is not recommended for all patients. Previous studies have suggested that thermal ablation may be effective for benign and malignant thyroid tumors. The goals of the current systematic review and meta-analysis were to comprehensively assess the efficacy and safety of the various thermal ablation techniques for the treatment of PTMC.

The researchers completed a search in the PubMed, MEDLINE, and EMBASE databases for studies reporting the safety and efficacy of radiofrequency, laser, and microwave ablation for PTMC. They focused on retrospective and prospective observational studies that included ≥5 patients and reported details on treatment outcomes.

The primary outcomes were the pooled proportions of complete disappearance of nodule, recurrence of nodule, overall and major complications, and pooled estimates of mean nodule volume reduction rates.

Of the 105 articles identified on the initial literature search, the full texts of 13 articles were thoroughly reviewed and the meta-analysis included 11 articles (7 retrospective, 2 prospective, and 2 studies with unclear design) with a total of 715 patients with 748 primary PTMCs (mean ages, 42.2-59.5 years; mean largest carcinoma diameters, 1.8-7.3 mm) and mean follow-up periods ranging from 7.8 to 25.7 months.

The pooled estimate of mean volume reduction was 73.5 mm3 (95% CI, 52.4-94.6), and the pooled estimate for mean volume reduction rate of PTMC after thermal ablation was 98.1% (95% CI, 96.7-99.5).

Of all the nodules, 415 completely disappeared after treatment. The pooled proportion of complete disappearance was 57.6% (95% CI, 35.4-79.8), although significant heterogeneity was noted for the percentage of complete disappearance of nodules (P <.001). The pooled proportion of recurrence was 0.4% (95% CI, 0-1.1).

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In total, there were 34 complications. These included 11 major complications (1.5%), all of which were related to voice changes that were transient in most cases (n=10). In addition, there were 23 minor complications, including moderate pain (3 cases), abnormal hormone levels (2 cases), hematomas (11 cases), and immediate hoarseness (7 cases). Other than the moderate pain relieved by medication, all minor complications resolved spontaneously within 3 months. The pooled proportion of major complications was 0.7% (95% CI, 0-1.5; I2 =0%). The pooled proportion of overall complications was 3.2% (95% CI, 1.1-5.2; I2 =34%).

Subgroup analysis according to treatment modality showed that there were no significant differences between modalities for complete disappearance of nodules (P =.351). While there were no significant differences between modalities for overall and major complications, radiofrequency ablation showed the highest volume reduction rate (99.3%), followed by microwave ablation (95.3%) and laser ablation (88.6%; P <.001).

The researchers acknowledged that the included studies were regionally concentrated in Asia and relatively small in number, which may have limited the findings of the meta-analysis. In addition, they did not have data on the operators’ experiences.

“Our results suggest that thermal ablation techniques have reasonable safety and efficacy profiles. However, future research needs to investigate studies with longer follow-up and more heterogeneous populations,” concluded the researchers.

Reference

Choi Y, Jung SL. Efficacy and safety of thermal ablation techniques for the treatment of primary papillary thyroid microcarcinoma: a systematic review and meta-analysis [published online February 4, 2020]. Thyroid. doi:10.1089/thy.2019.0707