Reassessment of Declines in Pulmonary Function ≥ 1 Year After Stereotactic Body Radiotherapy

Background Stereotactic body radiation therapy (SBRT) is standard care for patients with inoperable early-stage non-small cell lung cancer. However, clinicians may hesitate to use SBRT in patients with severe COPD because of potential negative effects on pulmonary function. We quantitatively analyzed long-term declines in pulmonary function after SBRT to ascertain lifelong tolerability to SBRT. Methods Between 2005 and 2010 at Ofuna Chuo Hospital, 292 patients with lung tumors were treated with SBRT. Among them, patients who underwent pulmonary function tests (PFTs) both pretreatment and at ≥ 1 year after SBRT were evaluated in this retrospective analysis. The decline ratio in FEV1 and FVC was assessed (ie, ΔFEV1 /preFEV1 and ΔFVC/preFVC). Predictors were identified using univariate and multivariate analyses. Results The 141 eligible patients had follow-up PFTs at a median of 21.0 (range, 12.0-74.8) months after SBRT. Among groups with normal function, or mild to moderate or severe COPD, the median values for ΔFEV1 /preFEV1 were 7.9%, 7.9%, and 7.4%, respectively, and for ΔFVC/preFVC, 5.1%, 3.4%, and 0.5%, respectively. Low BMI was the only predictor for ΔFEV1 /preFEV1 > 10%. Low BMI, high lung volume receiving ≥ 20 Gy, and high pretreatment FVC were predictors for ΔFVC/preFVC > 10%. Conclusions Declines in FEV1 and FVC were small, but statistically significant in patients with normal function or mild to moderate COPD, but nonsignificant in patients with severe COPD. These declines were primarily due to physiologic aging. SBRT had a limited effect on decline in long-term pulmonary function and may be an acceptable alternative to surgery for patients with comorbid lung cancer and COPD.