Intrafraction target shift comparison using two breath-hold systems in lung stereotactic body radiotherapy

•Surface-guided-based and spirometry-based deep-inspiration breath hold were accuracy-equivalent for intrafraction control.•Intrafraction shift was reduced when using spirometry-based than surface-guided-based deep-inspiration breath hold.•Higher superior-inferior shifts were found for patients with inferior lobe tumors.•Systematic and random intrafraction errors were higher for surface-guidance than for spirometry.