Stereotactic Radiotherapy for Multiple Lung Metastases: Early Clinical Outcomes

Introduction: Oligometastatic lung cancers are usually small in size and high doses of radiation increase the chance of local control. In this study, it was aimed to treat patients with stereotactic body radiotherapy (SBRT) technique and to examine the early effects of treatment in order to control these tumors of patients whose primary tumor was controlled but 3 and 4 metastases developed in their lungs. Methods: Computed tomography (CT) images of seven patients with three to four lung metastases were acquired using 2 mm sections. Treatment plans were prepared to deliver a total of 48 Gray (Gy) in four fractions at two isocenters. All plans were created using the Monaco treatment planning system (TPS) and the MonteCarlo algorithm at a filter-free 6MV energy (6FFF - dose rate: 1600 MU/min). During all these processes, the exact target was irradiated through active breathing control (ABC). Patients were administered a pulmonary function test (PFT) before and after the treatment and the results were compared. Results: 100% of the intended dose was prescribed to the tumor volumes of the patients. Critical organ doses met the TG101 standards. The maximum dose of the plans was kept below 120%. All treatment plans reached desired values and were clinically accepted. Conclusion: Local control was achieved in the patients and there was no grade 3-4-5 radiation pneumonia (RP). In particular, patients with severe pulmonary comorbidities should be carefully monitored for RP during the few months of follow-up after SBRT. Depending on the patient's condition (holding the breath, being stable, etc.) or the characteristics of the linear accelerator, SBRT can be safely administered to metastases at two or three isocenters and the metastases can be controlled when patients with locally controlled primary tumors develop multiple distant metastases in the lungs.