Treatment outcomes of patients with stage III non–small cell lung cancer and interstitial lung diseases receiving intensity‐modulated radiation therapy: A single‐center experience of 85 cases

OBJECTIVES: Whether curative‐intent radiotherapy could be safely applied to lung cancer patients with interstitial lung diseases (ILD) remains unclear. We aim to evaluate radiation induced lung toxicities (RILTs) and the efficacy of intensity‐modulated radiotherapy (IMRT) in these patients. ILD is characterized by inflammation or fibrosis in the interstitial tissue of the lung. MATERIALS AND METHODS: Stage III non–small cell lung cancer (NSCLC) and ILD patients treated with curative‐intent IMRT between 2010 and 2019 were retrospectively reviewed. Pre‐radiation computed tomography (CT) was scored according to a thin‐section CT scoring system for idiopathic pulmonary fibrosis. RESULTS: A total of 85 of 1261 stage III NSCLC patients were found with ILD. Seventeen (20%) of them developed G3+ (greater than or equal to grade 3) RILTs. The incidence abruptly dropped to 11.1%, 3.8%, and 0% for patients with honeycombing score ≤1, V20 <20%, or both, respectively. Multivariate analysis showed that honeycombing score >1 and V20 ≥20% were independently associated with higher risk of G3+ RILTs. The median overall survival (OS) and progression‐free survival (PFS) were 14.0 months and 7.4 months in the whole group, whereas 26.5 months and 10.6 months in the low‐risk group (patients with honeycombing score <1 and V20 <20%). In the univariate analysis for overall survival, G3+ RILTs were evaluated as risk factors (p = 0.026) and low‐risk group as the only protective factor (p = 0.063). In the multivariate analysis, G3+ RILTs were the only independent risk factor for OS. CONCLUSION: Honeycombing score >1 and V20 ≥20% were associated with high incidence of RILTs. However, patients with low risk might benefit from IMRT with acceptable toxicities and durable OS.