Stereotactic radiotherapy for stage I lung cancer: current results and new developments

In early stage non-small cell lung cancer (NSCLC), recent data from both prospective clinical trials and single institutions indicate that local control rates in excess of 88% can be achieved using stereotactic radiotherapy (SRT). Treatment-related toxicity is uncommon when "risk-adapted" fractionation schemes are applied, with lower dose per fraction used for larger tumors and when the planning target volume is in the proximity of critical structures. Both the superior outcome and convenience of fewer visits have led to a preference for SRT over conventional radiotherapy in countries such as Japan and the Netherlands. Reports on outcomes of SRT in patients unfit to undergo surgery may underestimate late toxicity as such patients have significant non-cancer related mortality. The evolution of technology has allowed for further improvements in the accuracy and speed of SRT delivery. Recent advances such as on-board imaging and intensity-modulated arc delivery techniques have improved treatment accuracy and tolerability, as well as the confidence of clinicians in applying SRT outside the setting of specialized tertiary institutions. Studies comparing primary surgery with SRT are underway, but the available data are compelling enough to allow SRT to be considered an established treatment option in patients who are aged 75 years and older, and in whom the estimated risks of postoperative mortality rates are high. The clinical development of SRT will be greatly facilitated by improvements in diagnostic procedures for peripheral pulmonary nodules. However, treatment without pathological confirmation may be justified in medically inoperable patients if the risk of malignancy is sufficiently high as to warrant an invasive diagnostic procedure.