Functional lung avoidance stereotactic body radiation therapy for central lung cancer patients

To improve patients' quality of life, it is necessary to preserve the high-functioning regions of the lung. This study aimed to propose a planning strategy that prioritizes sparing ventilation function for stereotactic body radiation therapy (SBRT) in patients with central lung cancer.

Twenty patients with central lung cancer were retrospectively enrolled. Ventilation maps were obtained from 4-dimensional computed tomography by deformable image registration and quantitative analysis. The top 60% and 30-60% of the total lung were defined as high- and medium-ventilation regions, respectively. Clinical plans and functional lung avoidance (FLA) plans were designed for each patient, and FLA plans were optimized to spare high-ventilation (H-V) regions. Dosimetric parameters were compared in terms of tumor coverage, plan heterogeneity, and dose of organs-at-risk (OARs). A patient-specific dose-function response model of Owen was applied to characterize personalized functional damage.

FLA plans led to significant reductions in the mean dose of H-V lung than in clinical plans (361.33 vs. 398.51 cGy, P<0.001), but at the expenses of degraded gradient index (4.95 vs. 4.58, P<0.001) and conformity index (0.82 vs. 0.86, P<0.05). Generalized estimated equations demonstrated the decreased risk of grade 2+ radiation pneumonitis (RP) by 1.51% (P<0.01), and grade 3+ by 0.39% (3.81% vs. 3.42%, P<0.01) for FLA plans. We also observed the average ventilation preservation for FLA as 0.17% (P=0.002) higher than clinical plans in one year after SBRT.

FLA plans can preserve the post-radiotherapy lung function, limit the pulmonary toxicity, and further improve life quality for SBRT patients with central lung cancer.