Assessment of lung tumor motion and setup uncertainties using implanted fiducials

Conclusions: Respiratory gating may be an effective method of reducing average motion during the course of treatment, but large motion is still possible when delivering gated treatment. Setup uncertainties were on the order of, if not larger than, residual gated motion. We recommend careful consideration of all sources of error before reducing margins on the basis of respiratory motion management alone without a strategy for accurate patient setup on a daily basis.