| Background and Purpose:Primary and metastatic lung cancers are all very common. However, most of them are unresectable on account of poor physiological or oncological conditions. This prompted the development of lung ablation techniques to enable local control of unresectable tumors. The most widely used technique is radiofrequency ablation (RFA). Compared with RFA, microwave ablation (MWA) is a less studied, but promising modality that may improve the efficacy of thermal ablation in the lung. It offers all the benefits of RFA as well as some other advantages, such as enlarged ablation zone, reduced procedure time, decreased heat-sink effect. However, MWA has never been systemically reported on major complications and seldom on efficacy with small series. The purpose of this study was to retrospectively evaluate the major complications and efficacies of MWA for lung tumors, reveal their characteristics and regularities, and facilitate the development of lung MWA.Materials and Methods:From January 2011 to May 2013,204 sessions of MWA were performed on 253 lung lesions of 184 consecutive patients with a mean age of 61.5±13.5 (range 19-85) years, including 72 female patients (35.3%,72/204) and 132 male patients (64.7%,132/204). The average maximum diameter was 3.3±1.93cm (0.5-12.Ocm). There were 150 cases of primary lung cancer (73.5%,150/204) and 54 cases of lung metastasis (26.5%,54/204). All tumors were diagnosed with direct or indirect pathologic evidence. The patients were not candidates for surgery because of previous pulmonary resection, poor cardiopulmonary status, multiple tumors, refusing surgery, or other reasons after discussion with thoracic surgeons.All procedures were performed with patients under local anesthesia and moderate sedation. Under the guidance of CT fluoroscopy, microwave antennae were placed into the tumor to perform ablation. If there was pneumothorax or pleural effusion that was enlarging or exceeded 35%-40%, or dyspneic or diminishing oxygen saturation, it would be treated with chest tube placement. At 24 hours after the procedure, each patient underwent non-enhanced chest CT scans to evaluate early complications. All patients were followed up at 1,3,6 and 12 months and thereafter at 6-month intervals with chest enhanced CT images and serum tumor markers.The criteria for major complications were in accordance with the classification proposed by the American Society of Interventional Radiology (SIR). All complications were evaluated on the basis of MWA procedures (204 sessions). Risk factors affecting major complications that were found in more than 1% of procedures were assessed.To facilitate the analysis of efficacy, combined with the characteristics of MWA, the primary lung cancer and metastatic lung cancer were grouped further, named stage group. The primary lung cancer patients were divided into 3 groups:group T had no regional lymph node or distant metastasis (T1-4N0M0); group N had no distant metastasis (T1-4N1-3M0) but had regional lymph node metastasis, group M had distant metastasis (T1-4M0-3M1). The patients with metastatic lung cancer were divided into 2 groups:solitary metastasis group had a solitary intrapulmonary metastasis while primary lesion had been removed and imaging examination showed no other metastatic lesions; multiple metastasis group had 2 or more intra-or extrapulmonary metastasis while the primary focus has been removed or not.Efficacies were evaluated on the basis of all cases except MWA related death (183 cases). To evaluate local efficacy, we adopted technical success rate, incomplete ablation rate, local progression rate and local progression-free survival (LPFS). To evaluate survival efficacy, we adopted remote progression-free survival (RPFS), cancer-specific survival (CSS) and overall survival (OS). Influential factors were statistically analyzed on incomplete ablation, local progression, RPFS and CSS.Results:Death related to the procedures occurred after 1 session (0.5%). Eighteen hours after the MWA for a lung adenocarcinoma lesion with a maximum diameter of 7.1 cm located in the left upper lobe, the 70-year-old man exhibited progressive dyspnea and chest X-ray showed a large pneumothorax with a pleural effusion. Chest tube placement and thoracic drainage alleviated the respiratory failure, but the patient died of sudden ventricular fibrillation 41 hours after the procedure.In the 204 MWA sessions, major complications developed after 42 sessions (20.6%), including 32 cases (15.7%) of pneumothorax requiring chest tube,6 cases (2.9%) of pleural effusions requiring chest tube,6 cases (2.9%) of pneumonia and 1 case (0.5%) of pulmonary abscess. Two of them had large pleural effusion and pneumonia sequentially. One of them had large pneumothorax and large pleural effusion sequentially. Two case (1.0%) of the large pneumothorax occurred at the same time with large subcutaneous emphysema, including 1 case (0.5%) caused by bronchopleural fistula. No delayed major complication was detected during the follow-up period. In the case of bronchopleural fistula, air leakage persisted after pleurodesis with video-assisted thoracoscope, till he died of brain metastasis 7 months later. All other major complications, except for the MWA related death, were cured after treatment.Univariate analysis suggested that male patients (P=0.011) and emphysema (P=0.0005) predisposed patients to chest tube placement for pneumothorax; a distance of<1 cm from chest wall to target tumor predisposed patients to chest tube placement for pleural effusion (P=0.015); and longer target tumor maximal diameter (P=0.040), more pleural punctures (P=0.001) and longer ablation time (P=0.006) were associated with higher pneumonia rates. Further multivariate analyses indicated the independent risk factors of chest-tube placement for pneumothorax included sex (P=0.047) and emphysema (P=0.004); the independent risk factor of chest tube placement for pleural effusion was distance from chest wall (<1/≥1cm) (P=0.013); and the independent risk factor of pneumonia was No. of pleural punctures (P=0.007). The technical success rate was 100% in the 204 sessions. The median follow-up period was 34.5±7.7 (range 24.7-51.8) months. The incomplete ablation rate evaluated at 1 month after the 183 first MWAs was 14.2%(26/183). Multivariate analysis suggested that maximum diameter (P<0.001) was the independent risk factor for incomplete ablation. The complete ablation rates in 0-3cm group,3.1-5cm group and>5cm group were 93.7%(89/95),82.3% (51/62) and 65.4%(17/26) respectively.The local progression rate was 19.1%(35/183). The 1-,2-,3-and 4-years LPFS rates were 81.8%,76.1%,74.1%and 74.1% respectively. Multivariate analysis suggested that maximum diameter (P<0.001) and emphysema (P=0.008) were the independent risk factors for local progression. The local progression rates in patients without and with emphysema were 15.5%(22/142) and 31.7%(13/41) respectively. The local progression rates in the 0-3cm group,3.1-5cm group and>5cm group were 7.4%(7/95),27.4%(17/62) and 42.3% (11/26) respectively.The remote progression rate was 62.8%(115/183). The median RPFS was 15.0 (95%CI: 11.1-18.9) months, and 1-,2-,3-and 4-years RPFS rates were 58.5%,36.0%,29.7%and 23.8% respectively. Multivariate analysis suggested that stage group (P<0.001) and incomplete ablation (P=0.002) were the independent risk factors for RPFS. The rate of cancer-specific death was 57.4%(105/183) and the rate of non-cancer-specific death was 4.4%(8/183). The median CSS was 24.9 (95% CI:19.9-29.9) months, and 1-,2-,3- and 4-years CSS rates were 85.0%,52.0%,37.5% and 31.1% respectively. The median OS was 23.7 (95% CI:20.6-26.8) months, and 1-,2-,3- and 4-years OS rates were 81.5%,49.4%, 35.7% and 29.6% respectively. Multivariate analysis suggested that stage group (P<0.001) and maximum diameter (P=0.009) were the independent risk factors for CSS.In the 138 cases of primary lung cancer admitted for survival analysis, the remote progression rate was 59.4%; the median RPFS was 16.5 (95% CI:11.3-21.7) months; the cancer-specific death rate was 52.9%; the non-cancer-specific death rate was 5.1%; the median CSS was 29.0 (95% CI:22.0-36.0) months and the median OS was 25.2 (9 18.1-32.3) months. In the 52 cases in group T, the 4-years RPFS, CSS and OS rate were 68.5%,80.0% and 76.9% respectively. In the 26 cases in group N, the median RPFS, CSS and OS were 15.0 (95% CI:7.3-22.7) months,26.1 (95% CI:10.3-41.9) months and 25.2 (95% CI: 14.0-36.4) months respectively. In the 60 cases in group M, the median RPFS, CSS and OS were 8.6 (95% CI:7.3-9.9) months,17.0 (95% CI:14.0-20.0) months and 15.9 (95% CI: 12.4-19.4) months respectively. In the 45 cases of metastatic lung cancer, the remote progression rate was 73.3%; the median RPFS was 12.1 (6.6-17.6) months; the cancer-specific death rate was 71.1%; the non-cancer-specific death rate was 2.2%; the median CSS was 19.4 (95% CI:12.0-26.8) months and the median OS was 18.7 (95% CI:12.1-25.3) months. In the 14 cases in solitary metastasis group, the median RPFS, CSS and OS were 30.3 (95% CI:17.9-42.7) months,38.3 (95% CI:18.6-58.0) months and 38.3 (95% CI:18.3-58.3) months respectively. In the 31 cases in multiple metastasis group, the median RPFS was 6.9 (95% CI:2.7-10.8), and the median CSS and OS were both 14.8 (95% CI:11.2-18.4) months.Conclusion:As a relatively safe modality, lung tumor MWA can induce major complications, but the indications for lung MWA need not be limited since most major complications were easy to handle. Enough attention should be paid to male patients, patients with emphysema, insufficient pulmonary function, subpleural or large target tumors.Lung MWA operation is relatively simple and owns high success rate. Local efficacies are excellent but become worse with the enlargement of target tumor. Survival efficacies of lung MWA are satisfactory for early stage NSCLC and solitary metastatic lung cancer, but need to be confirmed with further comparative study for primary lung cancer with regional lymph node or distant metastasis and metastatic lung cancer with multiple tumor lesions. Advanced stage, incomplete ablation and big target tumor predict short survival.Significance:The research productions of this study on major complications, efficacies and influential factors of lung MWA will help to facilitate the development of lung MWA. But the clear limitation accompanied with retrospective study makes our results demand confirmation from a multicenter study with larger patient series. |
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