Microwave Ablation of Stage IA Non-Small Cell Lung Cancers in US Veterans: Midterm Results

We describe early and midterm outcomes of microwave ablation (MWA) as primary therapy for early-stage non-small cell lung cancer (NSCLC) in a US veteran population

Materials and Methods:

Retrospective, single-institution, review of pulmonary ablations from 6/2016 to 9/2022 was conducted, identifying 122 ablations in 110 patients. Metastases, advanced stage NSCLC, treatments with cryoablation, and recurrences of prior surgical or radiation therapy for NSCLC were excluded (n=50). MWA was performed by a single operator using 2.45 GHz, gas-cooled system (NeuWave/Ethicon, Madison, WI). Technical success, ablation parameters, lesion characteristics, patient demographics, and adverse events were examined. Local recurrence-free survival (RFS) (progression within ablation zone), NSCLC progression free survival (PFS) and overall survival (OS) by were analyzed with Kaplan-Meier and Cox regression (SAS, Cary, NC).

Results:

MWA as primary therapy for stage IA NSCLC occurred in 60 patients (56 males, 4 females) with mean tumor size of 17.5 mm + 6.4 mm, stage IA1 (n=3), IA2 (n=38), IA3 (n=19); 37 adeno and 23 squamous cell carcinomas (SCC). All had been deemed unsuitable for or refused surgery/radiation. Technical success was 100%. Mean ablative energy was 499.9 J + 202.4 J. Discharge within 4 hours occurred for n=38, 63.3%. Chest tube placement accompanied ablation in the remaining n=22, 36.6%. One prolonged air-leak resolved at 20 days. No deaths or other major adverse events were observed. Typical follow-up consisted of 1 week chest x-ray, 1 month chest CT, and with chest CT or PET scans every 3-4 months. Median length of follow-up was 32.3 months (range, 1-68.5 months). Local recurrence free survival was 92%, 83%, and 80% at 1, 2, and 3 years respectively, with a median RFS >62.1 months. The 1, 2, and 3-year cancer PFS was 76%, 61% and 48%, respectively with a median PFS of 30.2 (95% CI, 19.9%, no upper bound). Median OS was estimated to be 45.2 months (95% CI, 36.4-56.9%). OS rates were 89%, 80%, and 66% at 1, 2, and 3 years, respectively. Cox regression analysis for age, cancer type, sex, size, cancer stage, and energy to lesion were not significant predictors of RFS, PFS, or OS when analyzed individually. However, when adjusted for sex, age at ablation, lobe of lung, size of cancer, and energy delivered to lesion, pathology type contributes to overall survival with SCC having a 2.5-fold increased risk of death over adenocarcinoma (P=0.035).

Conclusion:

Microwave ablation appears a safe, effective, and durable primary therapy for early NSCLC. Further study is warranted in comparative prospective trials.