Stereotactic body radiotherapy for early-stage non-small cell lung cancer in patients with subclinical interstitial lung disease.

Abstract

e21050 Background: Stereotactic body radiotherapy (SBRT) is a highly focused radiation treatment, which is now recommended to treat non-small cell lung cancer (NSCLC) patients with early stage disease. The purpose of this study is to evaluate the efficacy and toxicity of SBRT for early stage NSCLC patients with subclinical interstitial lung disease (ILD). Methods: One hundred and nine patients with early stage NSCLC were treated with SBRT between December 2011 and August 2016 in our institution; patients with subclinical (untreated and oxygen-free) ILD were treated with SBRT, while those with clinical ILD (post- or under treatment) were not. The median SBRT dose was 50 Gy in 5 fractions and the median biologically effective dose (BED; α/β = 10) was 100 Gy (range:72-119 Gy). The presence of subclinical ILD in the pre-SBRT CT findings was reviewed by two chest radiologists. The relationships among the efficacy, radiation pneumonitis (RP) and clinical factors were investigated. Results: Subclinical ILD was recognized in 38 (35%) of 109 patients. Grade 2–4 RP was recognized in 48 (44%) of 109 patients, no Grade 5 RP was happened. Grade 2–4 RP was observed in 17 (45%) of 38 patients with subclinical ILD. Subclinical ILD was not found to be a significant factor influencing Grade 2–4 RP; however, extensive RP beyond the irradiated field, including the contralateral lung, was recognized in only two patients who were both suffering from subclinical ILD, and the rate of extensive RP was significantly high in the patients with subclinical ILD. Dosimetric factors of the lungs (V5, V10, V20, MLD, V12.5, V13.5) were significantly associated with Grade 2–4 RP. The three-year overall survival and progression-free survival rates of all patients were 82.8% and 62.5%, respectively. No significant differences were seen in either overall survival or progression-free survival rates among the patients with ILD and those without ILD, or with RP and those without RP. Conclusions: Subclinical ILD was not found to be a significant factor for Grade 2–5 RP or clinical outcomes in early stage NSCLC treated with SBRT; however, uncommon extensive RP can occur in patients with subclinical ILD.