Baseline Pulmonary Function as a Predictor for Survival and Decline in Pulmonary Function Over Time in Patients Undergoing Stereotactic Body Radiotherapy for the Treatment of Stage I Non-Small-Cell Lung Cancer

Purpose: To examine the effect of baseline forced expiratory volume in 1 second (FEV₁) and diffusion capacity for carbon monoxide (Dl_co) on posttreatment survival and pulmonary function decrease after stereotactic body radiotherapy (SBRT) for patients with early-stage non-small-cell lung cancer (NSCLC). Methods and Materials: Seventy medically inoperable patients with Stage I NSCLC were treated with definitive SBRT to a dose of 6,000 (Stage IA) or 6,600 cGy (Stage IB), given in three equal fractions. Baseline and serial posttreatment pulmonary function data were collected. Results: Median age was 70.5 years, and median follow-up was 2.17 years. Median pretreatment FEV₁ and Dl_co were 1.05 L and 10.06 mg/min/mm Hg, respectively. There was no significant decrease in survival in patients with baseline FEV₁ and Dl_co less than the median value and less than the lowest quartile, whereas patients with values greater than the highest quartile of baseline FEV₁ had significantly inferior survival. There was no significant effect of pretreatment FEV₁ or Dl_co on posttreatment levels. There was a statistically significant decrease in Dl_co of 1.11 mg/min/mm Hg/y. Conclusions: Poor baseline pulmonary function did not predict decreased survival or pulmonary function after treatment. A statistically significant decrease in Dl_co after treatment was seen, similar to decreases seen in studies delivering standard thoracic radiotherapy. We conclude that low pretreatment FEV₁ and/or Dl_co alone should not be used to exclude patients with NSCLC from treatment with SBRT.