Outcomes of Percutaneous Microwave Ablation of Pleural Adjacent Lung Masses Under Moderate Sedation

Purpose: Percutaneous microwave ablation (MWA) is a suitable therapy for primary and metastatic lung cancer per recent guidelines {1}. Data specific to MWA for pleural adjacent lesions is lacking. We examined differences in lung MWA outcomes, sedation requirements, and self-reported pain stratified by proximity to lung pleura.

Materials and Methods: An IRB-approved, retrospective, single-institution review of lung MWA from 1/2016 to 6/2022 was performed. Exclusion criteria included incomplete sedation records and single-session ablation of multiple lung masses. Demographics, tumor location, sedation dosages, pain scores, pneumothorax (PTX) +/- chest tube, adverse events, and local tumor recurrence (LTR) were aggregated. MWA was performed by a single operator with 2.45 GHz MWA 17g antenna system (NeuWave/Ethicon, Madison, WI). Sedation was administered by radiology nurses under physician supervision. If anticipated ablative margins included the pleura, 10-20mL of local anesthesia (1% lidocaine and 0.5% bupivacaine) was introduced to the pleural edge. VAS (1-10) was used to assess for pain. Masses were subdivided by distance to nearest pleural surface/fissure: Pleural (touching, 0mm), subpleural (1-10mm), and central ( >1cm). Kruskal-Wallis 1-way ANOVA compared sedation parameters and pain level. PTX/chest tube and LTR were analyzed via chi-square test.

Results: 81 patients undergoing 96 lung MWA met inclusion criteria. No significant demographic differences were observed: pleural (n=23), subpleural (n=28), and central (n= 45). No significant differences among sedation or pain scores: mean 128 ± 61 mcg fentanyl (p=0.13); 2.4 ± 1.1 mg midazolam (p=0.33); VAS between pleural, subpleural, and central groups (3.3, 2.1, 1.7, p=0.122). No significant difference in rates of PTX: 35% pleural (n=8), 46% subpleural (n= 13), 49% central (n=22). No significant difference (p=0.53) for chest tube placement: 30% pleural (n=7), 29% subpleural (n=13), 40% central (n=18). If required, no significant differences observed in duration of chest tube/length of stay between pleural, subpleural, and central groups (p=0.46). 8 prolonged air leaks occurred out of 96 ablations (8.3%) in pleural (n=2), subpleural (n=1), and central (n=4) groups. 1-year local tumor recurrence was 13% (n=3), 7.1% (n=2), and 6.7% (n=3) of pleural, subpleural, and central groups respectively (p=0.64).

Conclusion: Percutaneous microwave ablation under moderate sedation is safe, effective, and well-tolerated for primary and metastatic lung nodules regardless of proximity to lung pleura.