Radiation pneumonitis (RP) after stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC): A prospective, observational study.

Abstract

e21065 Background: RP is a clinically challenging side effect following SBRT. The reported incidence of RP varies from 2.2% to 46.8%, depending on study design and different grading systems. We evaluated the grading systems for RP and identified possible predictive tests for RP. Furthermore, we estimated the correlation between RP and dosimetric measurements from the radiation therapy. Methods: Medically inoperable patients, n = 44, with peripherally located NSCLC stage I-II, were treated with SBRT, with a total dose of 45–56 Gy in 3–8 fractions. Median age was 75 years, 43.2% were female and 60% had moderate to very severe COPD. Follow up included physical examination by pulmonologist, spirometry and single-breath lung diffusing capacity (DLCO) and CT evaluation at baseline and 1.5, 3, 6, 9 and 12 months after SBRT. Results: We constructed three groups for grading RP based on CTCAE version 5.0 and imaging changes according to EORTC (LENT-SOMA) Non-RP (asymptomatic or mild symptoms and slight imaging changes, n = 19, 43%), Asymptomatic, radiology-only RP (asymptomatic or mild symptoms, increased density imaging changes, n = 17, 39%) and Symptomatic and radiology-detected RP (moderate and severe symptoms and increased density imaging changes, n = 8, 18%). Active smokers and patients with emphysema were overrepresented in non-RP group. In the symptomatic RP group, DLCO and FEV1 dropped almost 5% 4-6 weeks after SBRT, before symptoms and imaging changes, and DLCO, FVC and FEV1 dropped significantly at 3 months (table). Development of RP was associated with critical dose-volume parameter 1000ccm and 1500ccm. Several dosimetric parameters significantly negative correlate with FVC-drop at 1 and 3 months only in symptomatic RP. Conclusions: Active smokers and patients with emphysema have less propensity of RP. Symptomatic RP is seen with a presymptomatic drop in FEV1 and DLCO occurring 4-6 weeks after SBRT. Critical dose-volume parameter is important parameters for RP. Correlation between dosimetric parameters and FVC-drop in symptomatic RP. Clinical trial information: NCT02428049 . [Table: see text]