Is There a Lower Limit of Pretreatment Pulmonary Function for Safe and Effective Stereotactic Body Radiotherapy for Early-Stage Non-small Cell Lung Cancer?

Introduction: To evaluate the influence of pretreatment pulmonary function (PF) on survival, early and late pulmonary toxicity after stereotactic body radiotherapy (SBRT) for early-stage non-small cell lung cancer. Methods: Four hundred eighty-three patients with 505 tumors of early-stage non-small cell lung cancer cT1-3 cN0 were treated with image-guided SBRT at five international institutions (1998-2010). Sixty-four percent of the tumors were biopsy-proven and 18F-fluorodeoxyglucose-positron emission tomography was performed for staging in 84%. Image-guided SBRT was performed with a median of three fractions to a median total dose of 54 Gy. Pretreatment PF was available for 423 patients, and 617 posttreatment PF tests from 270 patients were available. Results: A large variability of pretreatment PF was observed: the 90% range of forced expiratory volume in 1 second and diffusing capacity for carbon monoxide was 29 to 109% and 5.5 to 19.1 ml/min/mmHg, respectively. PF was significantly correlated with overall survival but not cause-specific survival: diffusing capacity for carbon monoxide of 11.2 ml/min/mmHg differentiated between 3-year overall survival of 66% and 42%. Radiation-induced pneumonitis grade >= II occurred in 7% of patients and was not increased in patients with lower PF. A significant and progressive change of PF was observed after SBRT: PF decreased by 3.6% and 6.8% on average within 6 and 6 to 24 months after SBRT, respectively. Changes of PF after SBRT were significantly correlated with pretreatment PF: PF improved for worst pretreatment PF and the largest loss was observed for best pretreatment PF. Conclusions: Image-guided SBRT is safe in terms of acute and chronic pulmonary toxicity even for patients with severe pulmonary comorbidities. SBRT should be considered as a curative treatment option for inoperable patients with pretreatment PF as reported in this study.