Margin calculation for multiple lung metastases treated with single-isocenter SBRT

Highlights: • Safety margin calculation for single-isocenter SBRT of multiple lung metastases. • Relative inter-lesion motion is compensated by an additional 1 mm margin. • Pleural attachment is characterized with reduced inter-lesion position variation. • For 65% dose prescriptions, random errors contribute to the margin only in SI. A single-isocenter stereotactic body radiotherapy (SBRT) approach for multiple lung metastases has the potential to lower cumulative patient dose and reduce overall treatment time. However, the magnitude of inter-lesion position variation is currently unknown and not incorporated in margin calculations. The aim of this study was to quantify inter-lesion position variation and calculate safety margins for single-isocenter lung SBRT.