RFA has been used to ablate primary lung tumors as well as a multitude of pulmonary metastases. In fact, most publications reported a mixed bag of pathology. In addition, reported recurrence rates vary in definition. Most surgical publications relating to surgical resection consider regional lymph nodes as a recurrence, whereas, in most radiologic reports, recurrence is only measured at the site of the tumor. Hence, overall recurrence rates must be viewed more closely. A review of 17 publications reported a complete ablation rate of 90% ranging from 38% to 97%.21 Tumors <2 cm in size had higher rates of complete ablation.22,23 As tumor sizes increase, rates of tumor ablation tend to decrease. Lee et al.24 noted ablation rates of 38% in tumors 3 to 5 cm and 8% for those larger than 5 cm. Simon reported a statistically significant difference in tumor progression for tumors <3 cm compared to those >3 cm (p = 002).25 The 1-year progression-free rate was 83% for tumors <3 cm versus 45% for those >3 cm. At 3 years, it was 57% versus 25%. Median time to progression was 12 months for larger tumors versus 45 months. Lee notes that all tumors <3 cm had a complete response with a survival of 19.7 months in complete responders versus 8.7 months in partial responders.24 Herrera reported a complete or partial response in 67% of tumors smaller than 5 cm but only 33% control for those >5 cm.26
Others have demonstrated that when the ratio of ablation volume to tumor volume was ≥3, the complete ablation rate at 1 year was 83% compared to 61% when the ratio was <3.22 In fact, a margin of 4.5 mm of ground glass opacity surrounding the tumor zone results in a complete ablation.27 As most catheters extend to a 5 cm diameter, tumors <3 cm are best treated to provide the 0.5 cm to 1 cm margin of additional tissue ablation. In addition, electrode configuration may have an effect on recurrence with a lower success rate for the straight electrode, such as the LeVeen, compared with the expandable electrode, although this difference may be more related to tumor location than electrode selection.22
A prospective multicenter intent to treat study (RAPTURE) was published in 2008.28 The study included 106 patients with 183 treated tumors. Complete response at 1 year was 88%. Lung cancer patients had 1- and 2-year survivals of 70% and 48%, respectively. Most of these patients were at high risk and died of non–cancer-related diseases. Stage I patients had a 2-year survival of 75% and a cancer-specific survival of 92%.
Simon et al.25 reported on 75 primary non–small-cell lung cancer (NSCLC) cases, stages IA and IB, treated with RFA. Median survival was 29 months. The 1-, 2-, 3-, 4-, and 5-year survivals were 78%, 57%, 36%, 27%, and 27%, respectively. With smaller tumors <3 cm, the progress-free survival rate was 47% at 5 years. Fernando29 reported a mean survival of 21 months for NSCLC patients with a median progression-free survival of 18 months. Beland30 demonstrated a 23-month, disease-free survival. Of the recurrences, 38% were local, 18% intrapulmonary, 18% nodal, and 21% distal. Zemlyak31 compared RFA to surgical resection for stage I lung cancer. The 3-year survival was 87.1% for surgery and 87.5% for RFA.
Similar survival rates have been reported for metastatic disease, although extrathoracic metastasis is an independent factor in overall survival.32 Several studies looking at colorectal metastasis reported a 2-year survival rate of 64% to 78%.15,32 The RAPTURE study reported a 1-year survival of patients with colorectal metastasis of 89% and 2-year survival of 66%.28 Simon noted a 1-year survival of 87%, and 3- and 5-year survival of 57% for colorectal metastasis.25 Other studies have demonstrated higher 1-year survival at 95% and 3-year survival at 50%.33 For sarcoma, renal cell, and head and neck cancers, 5-year survival is in the range of 45% with disease-free survival of 36 months or more.34
Overall lung function is preserved. Baere evaluated PFTs at 1 month and showed no difference between pretreatment and posttreatment function.15 Lencioni also saw no difference in pulmonary function at 12 months.28 In addition, Lee noted good symptom control in noncurative patients who had hemoptysis (80%), chest pain (36%), and cough (25%).24
Lee et al.35 evaluated the utility of RFA as an adjuvant treatment for lung cancer. Patients with stage III and IV disease were treated with either chemotherapy alone or chemotherapy and RFA. Survival for the chemotherapy alone was 29 months. Those who received both chemotherapy and RFA had a survival of 42 months (p = 0.03). Although a small study, there may be some utility in using RFA in the adjuvant setting.