Potentially curative stereotactic body radiation therapy (SBRT) for single or oligometastasis to the lung

Background. To analyze the treatment outcomes of a potentially curative therapy, stereotactic body radiation therapy (SBRT), for patients with single or oligometastasis to the lungs. Material and methods. Sixty-seven metastatic lung lesions in 57 patients were treated with SBRT between September 2001 and November 2010. All patients had single or oligo-metastasis to the lungs following a meticulous clinical work-up, including PET-CT scans. The lungs were the most common primary organ (33 lesions, 49.3%), followed by the head and neck (11 lesions, 16.4%), the liver (nine lesions, 13.5%), the colorectum (seven lesions, 10.4%), and other organs (seven lesions, 10.4%). Three different fractionation schedules were used: 50 Gy/5 fractions to four lesions (6.0%); 60 Gy/5 fractions to 44 lesions (65.7%); and 60 Gy/4 fractions to 19 lesions (28.3%). Results. Local tumor progression occurred in three lesions (4.5%). The three-year actuarial local control rate was 94.5%. Tumors larger than or equal to 2.5 cm showed poorer local control (98.3% vs. 77.8%, p <0.01). Metastatic tumors from the liver and colorectum showed lower local control rates than those from other organs (77.8%, 85.7%, and 100%, p = 0.04). The two-year overall survival rate was 57.2%. Patients with tumors smaller than 2.5 cm had more favorable survival rates (64.0% vs. 38.9% at two-year, p = 0.032). Patients with extrathoracic disease had poorer survival rates (66.1% vs. 0% at two-year, p = 0.003). Patients with disease-free intervals longer than two years showed a trend toward good prognosis (71.1% vs. 51.1% at two-year, p = 0.106). Grade 2 lung toxicity occurred in four patients (6.0%). One patient experienced Grade 5 lung toxicity following SBRT. Conclusion. SBRT for single or oligo-metastasis to the lung seems quite effective and safe. Tumor size, disease-free interval, and presence of extrathoracic disease are prognosticators for survival.