Microwave ablation vs. surgery for thyroid microcarcinoma near the capsule: a propensity-matched study on safety and efficacy.

Objective: Ultrasound-guided microwave ablation (MWA) has been widely used as an efficient and safe minimally invasive treatment for papillary thyroid microcarcinomas (PTMCs). However, controversy persists regarding its application for PTMCs adjacent to the thyroid capsule. This study aimed to compare the feasibility, efficacy, and safety of MWA versus surgery for US-detected PTMCs closely abutting the capsule. Materials and methods: This retrospective study included 364 PTMC patients from January 2019 to September 2024, comprising 69 in the MWA group and 295 in the surgical group. Propensity score matching (PSM) was used to balance baseline characteristics between groups. Based on maximum nodule diameter, patients were stratified into ≤5 mm and >5mm subgroups. Primary outcomes included technical success, postoperative complications, and tumor progression; secondary outcomes encompassed changes in tumor size/volume and treatment-related variables (hospital stay, operative duration, estimated blood loss, and costs). Results: After PSM, 94 patients underwent surgery (mean age 43.89±11.50 years) and 67 received MWA (mean age 45.27±10.66 years). Follow-up durations were 31.00±1.66 (MWA) and 31.57±16.00 months (surgery). Both groups achieved 100% technical success, with no significant difference in complication rates (3.0% vs. 3.3%, P = 1.000). Tumor progression occurred in one case per group (1.1% [1/94] vs. 1.5% [1/67], P > 0.05). Among surgery patients without preoperative US-detected lymph node metastasis (LNM), pathology revealed LNM in 40.4% (38/94), primarily in central compartments (86.8%, 33/38). However, only one surgical case (1.1%) exhibited LNM during follow-up, while no MWA patients developed LNM or required delayed surgery. Secondary outcomes favored MWA over surgery, showing shorter operative time (32.18±6.31 vs. 73.88±31.8 min, P < 0.001), less blood loss (1.94±0.42 vs. 14.73±14.03 mL, P < 0.001), reduced hospitalization (2.81±2.42 vs. 6.57±2.50 days, P < 0.001), and lower costs (17,013.57±3,975.02 vs. 26,610.61±4,474.84 CNY, P < 0.001). The cumulative tumor disappearance rate in the MWA group was 89.0%. Subgroup analyses revealed no significant differences in treatment variables, complications, or tumor volume reduction. Conclusion: MWA demonstrates comparable short-term outcomes to surgery for PTMCs adjacent to the capsule, offering a safe and effective therapeutic alternative.