Patients with sarcoma and lung metastases have few therapeutic options, with poor response to systemic treatment. Many of them are not eligible to surgical treatments due to the high number and distribution of pulmonary lesions or due to comorbidities, which reduce the survival chances of these individuals. Given the high efficacy and overall increased survival demonstrated by recent studies, the minimally invasive treatments (mainly radiofrequency ablation) have gained ground. Although the microwave ablation is a promising new technique for the treatment of patients with pulmonary metastases, there are few studies in the literature to evaluate the efficacy and safety of this procedure in the above population.

This study was designed to prospectively evaluate the safety and effectiveness of microwave ablation therapy in the treatment of metastatic lung lesions secondary to sarcoma. This technique has been proven to be successful in producing greater areas of ablation, increasing the chances of success and reducing the possibility of local recurrence, especially when compared to radiofrequency ablation. There will be 60 consecutive patients diagnosed and treated at the oncology clinic at the São Paulo State Cancer Institute that are going to participate in this study, after meeting the inclusion/ exclusion criteria. This number may be increased up to approximately about 20 patients, according to the sample behavior in the initial analysis and follow-up. All patients will be informed about the benefits, risks, complications and limitations related to the procedure and written informed consent will be applied. Patients will also be informed that microwave ablation is a new technology in Brazil, despite the extensive international experience and the results already validated in the medical literature.

Logistic regression will be used to evaluate the success of the microwave ablation according to the characteristics of the lesion before the procedure. Logistic regressions for correlated data will be used to (a) evaluate the success of ablation according to all registered lesion characteristics, i.e., numeric characteristics (including tumor size and location) and categorical characteristics (histopathology of the primary tumor); (b) verify if combinations of two or more features of the lesions pose significant independent predictors for the success of ablation; and (c) construct a model to estimate the probability of success of the microwave ablation based on lesion characteristics before the procedure. The survival of patients will be assessed according to (a) the end result of the procedure (patients will be classified in two groups: an effective ablation group and a non-effective ablation group) and (b) the histopathological nature of the primary tumor. The survival rates will be calculated using the Kaplan-Meier test. The log-rank test (x² value of Cox-Mantel) will be used to determine statistically significant differences between the patients' survival rates. The value of P less than 0.05 will be considered to indicate a statistically significant difference for all analyses. Statistical software (Bias for Windows, version 8.4, Epsilon Verlag, Frankfurt, Germany) will be used.

Inclusion Criteria:

• Patients over 18 years;
• Patients with lung metastases arising from sarcoma;
• Patients who are not eligible for surgery for medical reasons, including limited cardiopulmonary reserve. In this cases we will perform a pulmonary function test (PFT) to determine if the patient can withstand ablation;
• Patients with recurrent metastases after pneumectomy or metastases after surgical resection. In this cases we will perform a PFT to determine if the patient can withstand ablation;
• Patients with pulmonary lesions with dimensions up to 3,0 cm in the largest axial diameter;
• Patients with four or fewer lesions. In cases of bilateral metastases, we will evaluate the treatment of only one lung at a time, with an interval of at least two weeks for the treatment of the contralateral lung, respecting the clinical evolution of the patient.
• Patients with no extrapulmonary metastases or just indolent extrapulmonary disease;
• Patients with prior histopathological confirmation of pulmonary lesions.

Exclusion Criteria:

• Patients with primary disease without clinical control;
• Presence of uncontrolled extrapulmonary disease, including lymph node progression;
• Presence of hilar lesions or near the main bronchi;
• Presence of five or more lung lesions and/or lesions larger than 3,0 cm in greatest axial length;
• Presence of tumors infiltrating the chest wall, mediastinal and/or pleural dissemination;
• Patients with severe coagulopathy (international normalized ratio (INR) > 1,5 or lower platelet count to 50000/mm³);
• Patients with chronic obstructive pulmonary disease (COPD) stage III/ IV;
• Patients with septicemia;
• Patients refusing ablation treatment or participation in the study.

There is not a plan to make IPD available