Evaluation of Pulmonary Functions by Spirometry after Stereotactic Body Radiotherapy in Lung Tumors

Abstract

Introduction: To evaluate changes in pulmonary function by spirometry after stereotactic body radiotherapy (SBRT). Methods: A single-center, retrospective study was performed which analyzed lung function after SBRT from January 1, 2015 to January 31, 2020. Eligible patients were ≥18 years of age, with early-stage lung cancer or lung metastases ≤5 cm and Karnofsky performance status (KPS) >70. Patients were excluded if they had a history of non-infectious pneumonitis or interstitial lung disease. Clinical cases were discussed in a multidisciplinary tumor board, and the patients were classified as surgically resectable but medically inoperable. Mixed-effects models were used to evaluate changes in forced expiratory volume in 1 (FEV1), forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO) at 3, 6, 12, and 24 months after SBRT. Results: Fifty-two patients underwent SBRT. Median follow-up spirometry post-SBRT was 12 months (range, 12-24). No significant differences were observed during the first year in both liters and the percentage of predicted FEV1 evolution. A gain of 5.9% [95% CI, 2.3; 9.6 percent (p=0.0014)] was beheld after 24 months post-SBRT. Although, no significant difference has been viewed when we analyze it in liters with an FEV1 value 24 months post-SBRT of 1.57 liters [95% CI, 1.56; 1.59 liters (p=0.848)]. There are no differences when we analyze FVC evolution according to liters during the first two years post treatment. Finally, no differences were observed when analyzing DLCO evolution according to percentage or as ml/min/kPa. Conclusions: SBRT in primary lung tumors or pulmonary metastases does not negatively influence pulmonary function assessed by spirometry at least in the first two years after treatment.