Microwave Ablation of Primary and Secondary Lung Malignancies

Surgery is the first choice of treatment for early-stage primary pulmonary malignancies, but up to 15% of all patients, and 33% of patients greater than 75 years of age, are not surgical candidate's due to locally advanced disease, poor cardiopulmonary reserve and significant medical co-morbidities. Some patients are also unwilling to undergo surgery. This has prompted the development of alternatives to surgery so that local control of unresectable tumors can be achieved. Stereotactic body radiation therapy (SBRT) is currently an alternative therapy for these patients with 3-year survival rates of between 42 and 60%. SBRT has excellent local control rates and a favorable toxicity profile relative to other surgical and non-surgical therapies. Radiation pneumonitis (RP), amongst others, is one of the major toxicities which can limit the maximal radiation dose that can be safely delivered to thoracic tumors. Reported rates of SBRT induced RP requiring clinical intervention range from 0% to 29% and life-threatening toxicities have been reported in up to 12% of cases in various studies. The potential for toxicities from SBRT could limit the number of times a patient could be treated with SBRT for residual, recurrent or new pulmonary lesions over time. Following the first report of thermal ablation for lung malignancies in 2000, this modality has been used to treat primary and secondary malignancies and has emerged as an effective, low-cost, safe and repeatable alternative to SBRT for local tumour control. The most widely practised technique is radiofrequency ablation (RFA). Microwave ablation (MWA) is a relatively new therapy and offers all the advantages of RFA, but with significant additional advantages 3. These include reduced procedure times, lower complication rates, increased ablative temperatures, improved propagation of thermal energy particularly in the lung, improved efficacy in lesions that are in close proximity to blood vessels due to reduced heat-sink eff