Stereotactic body radiotherapy for stage I lung cancer and small lung metastasis: evaluation of an immobilization system for suppression of respiratory tumor movement and preliminary results

Background: In stereotactic body radiotherapy (SBRT) for lung tumors, reducing tumor movement is necessary. In this study, we evaluated changes in tumor movement and percutaneous oxygen saturation (SpO(2)) levels, and preliminary clinical results of SBRT using the BodyFIX immobilization system. Methods: Between 2004 and 2006, 53 consecutive patients were treated for 55 lesions; 42 were stage I non-small cell lung cancer (NSCLC), 10 were metastatic lung cancers, and 3 were local recurrences of NSCLC. Tumor movement was measured with fluoroscopy under breath holding, free breathing on a couch, and free breathing in the BodyFIX system. SpO(2) levels were measured with a finger pulseoximeter under each condition. The delivered dose was 44, 48 or 52 Gy, depending on tumor diameter, in 4 fractions over 10 or 11 days. Results: By using the BodyFIX system, respiratory tumor movements were significantly reduced compared with the free-breathing condition in both craniocaudal and lateral directions, although the amplitude of reduction in the craniocaudal direction was 3 mm or more in only 27% of the patients. The average SpO(2) did not decrease by using the system. At 3 years, the local control rate was 80% for all lesions. Overall survival was 76%, cause-specific survival was 92%, and local progression-free survival was 76% at 3 years in primary NSCLC patients. Grade 2 radiation pneumonitis developed in 7 patients. Conclusion: Respiratory tumor movement was modestly suppressed by the BodyFIX system, while the SpO(2) level did not decrease. It was considered a simple and effective method for SBRT of lung tumors. Preliminary results were encouraging.