Stereotactic ablative radiotherapy (SABR) for early-stage central lung tumors: New insights and approaches.

The use of stereotactic ablative radiotherapy (SABR) for central lung tumors is increasing. Centrally located lung tumors can be subdivided into two categories, namely the 'moderately central' tumors where the planning target volume is located within 2 cm of the proximal bronchial tree, and the 'ultracentral' tumors where a planning target volume (PTV) overlaps the trachea or main stem bronchi. The toxicity of SABR appears acceptable when 'moderately central' tumors are treated using techniques that comply with organs at risk tolerance doses used for prospective trials and in recent publications. A high toxicity is seen when ultracentral tumors are treated using SABR, and conventional radiotherapy appears more appropriate in such tumors as the true normal organ tolerance doses remain unknown. When ultracentral tumors are treated with non-SABR hypofractionated radiotherapy, a homogenous dose distribution in the planning target volume and limitation of both normal organ maximum point doses and volumes receiving high doses seems to be needed.