Long-term pulmonary function decline after stereotactic body radiation therapy for lung tumors

Stereotactic body radiation therapy (SBRT) is widely used for early-stage lung cancer and inoperable cases due to its high local control rate and limited invasiveness. However, its long-term impact on pulmonary function remains controversial.

We retrospectively analyzed patients with lung tumors who underwent SBRT at our institution between November 2009 and May 2024 and had at least one pulmonary function test (PFT) before and after treatment. Patients with prior thoracic radiotherapy or post-treatment events affecting lung function were excluded. PFT changes were assessed at multiple post-treatment intervals. Lung dose parameters and correlations with changes in PFT results were analyzed. Receiver operating characteristic (ROC) analysis was used to determine dose cut-off values predictive of a ≥ 10% decline in pulmonary function.

A total of 61 patients were included. Significant declines in vital capacity (VC), forced vital capacity (FVC), and forced expiratory volume in 1 second (FEV₁) were observed only in the very late phase (> 24 months post-SBRT). VC and FVC decline correlated negatively with D33.3%, and FEV₁ decline correlated most strongly with V20. ROC analysis identified D33.3% and V20 thresholds that significantly predicted ≥ 10% decline. Patients above these dose thresholds showed significantly greater reductions in all three parameters.

Pulmonary function decline after SBRT becomes evident more than 2 years post-treatment and is associated with specific lung dose parameters. These findings highlight the importance of long-term monitoring and careful dose planning in SBRT for lung tumors.