Impact of palliative radiotherapy with or without lung irradiation in patients with interstitial lung disease.

BACKGROUND AND PURPOSE: Acute exacerbations or acute lung injury, including radiation pneumonitis (AE-ALI/RP) of interstitial lung disease (ILD), has a fatal prognosis. We evaluated the risk of palliative-intent radiotherapy (RT), with or without lung irradiation, for AE-ALI/RP of ILD. MATERIALS AND METHODS: The data of patients with ILD who received palliative-intent RT between January 2011 and January 2022 were retrospectively reviewed. Factors associated with AE-ALI/RP grade ≥ 3 were assessed using univariate and multivariate analyses. RESULTS: One hundred and three patients were examined, with median imaging and survival follow-up times of 88 (2-1440) and 144 (8-1441) days. The median time to onset of AE-ALI/RP grade ≥ 3 was 72 (5-206) days. In multivariate analysis, a higher pulmonary fibrosis score (PFS ≥ 3) (hazard ratio, HR: 2.16; 95% confidence interval, CI: 1.36-3.43; p < 0.01) and lung irradiation (lung-RT) (HR: 3.82; 95% CI: 1.01-15.73; p = 0.04) were significant factors for AE-ALI/RP grade ≥ 3. In patients who received lung-RT, the 100-day survival rate and cumulative incidence of AE-ALI/RP grade ≥ 3 were 56.8% and 13.7%, respectively. In patients with PFS ≥ 3 and who underwent lung-RT, the 100-day cumulative incidence of AE-ALI/RP grade ≥ 3 was 37.5%; all patients with AE-ALI/RP grade ≥ 3 had grade 5. In patients with PFS ≥ 3 without lung-RT, the 100-day cumulative incidence of AE-ALI/RP grade ≥ 3 was 4.8%. CONCLUSION: High PFS and lung-RT are significant risk factors for AE-ALI/RP grade ≥ 3. Even with relatively low doses, palliative-intent lung-RT carries an extremely high risk of AE-ALI/RP when PFS is high.