Linear accelerator-based stereotactic body radiation therapy in the treatment of oligometastatic disease

The present study reports the clinical outcomes of hypofractionated stereotactic body radiation therapy (SBRT) for oligometastasis (OM) originating from various tumors. Between February 2012 and April 2017, 40 patients with unresectable OM were treated with SBRT. Of these patients, 92% showed a solitary nodal metastasis and the rest had up to three metastases. The dose prescription was 50 Gy in 10 fractions with three-dimensional conformal techniques or volumetric intensity-modulated arc therapy. Median follow-up was 14 months. Of the 40 patients, none showed local progression at the site of SBRT, but 20 patients showed tumor growth at distant sites during follow-up. The 2- and 3-year overall survival rates were 45.1 and 36.1%, respectively. The 2- and 3-year progression-free survival rates were 35.4 and 26.5%, respectively. The interval between diagnosis and detection of OM (<2 vs. >2 years) and primary tumor site (esophagus vs. others) emerged as significant variables affecting survival. Grade 3 subacute and grade 4 chronic toxicities were observed in 1 and 2 patients, respectively. SBRT of 50 Gy in 10 fractions for OM from various primary tumors was shown to lead to good clinical outcomes from the viewpoints of local control and toxicity frequency. However, additional studies are required to identify the patient groups likely to receive maximal benefits from such treatment.