Microwave Ablation Therapy: Clinical Utility in Treatment of Pulmonary Metastases

Purpose: To prospectively evaluate the safety and efficacy of microwave ablation therapy of unresectable pulmonary metastases.

Materials And Methods: All patients provided informed consent for this prospective institutional review board-approved study. Eighty patients (30 men, 50 women; mean age, 59.7 years ± 6.4; range, 48-68 years) underwent computed tomography-guided percutaneous microwave ablation of pulmonary metastatic lesions in 130 sessions. The tumors represented metastases from colorectal carcinoma, breast carcinoma, hepatocellular carcinoma, renal cell carcinoma, and bronchogenic carcinoma; there was no evidence of extrapulmonary metastasis for any tumor. Logistic regression analysis was used for evaluation of the statistical significance of factors affecting the end result of microwave ablation therapy. The Kaplan-Meier method was used for estimation of survival rates.

Results: Complete, successful ablation was achieved in 95 (73.1%) of 130 lesions. Successful tumor ablation was significantly more frequent for lesions with a maximal axial diameter of 3 cm or smaller (90 of 110) than for lesions greater than 3 cm in maximal axial diameter (five of 20) (P < .0001) and for peripheral lesions (80 [80%] of 100) than for centrally located lesions (15 [50%] of 30) (P = .002). The histopathologic type of the metastasis did not significantly correlate with the ablation result (P > .3). The 12- and 24-month survival rates were 91.3% and 75%, respectively. There was no intraprocedural death, and the overall 60-day mortality rate after ablation was 0%. Higher survival rates were observed in patients with tumor-free states after successful ablation than in patients with failed ablation (P = .001). The incidence of pneumothorax was 8.5% (11 of 130). An intercostal chest tube was applied in one (0.8%) of the 11 sessions. Pulmonary hemorrhage developed in eight (6.2%) of 130 sessions.

Conclusion: Microwave ablation therapy may be safely and effectively used as a therapeutic tool for treatment of pulmonary metastases. The efficacy of the treatment is primarily determined by preablation tumor size and location in relation to the hilum.