Exploring radiation pneumonitis mortality risk among patients with underlying lung disease.

e23138 Background: Radiation pneumonitis (RP) is an acute inflammatory reaction of the lung parenchyma following radiation therapy. Patients with interstitial lung disease (ILD) are at greater risk for RP compared to those with chronic obstructive pulmonary disease (COPD) or no lung disease, yet the impact of these conditions on inpatient mortality in lung cancer patients hospitalized for RP remains unclear. We hypothesized that mortality would be highest in patients with ILD and similar between patients with COPD and those without underlying lung disease. Methods: We conducted a retrospective cohort study using the Nationwide Inpatient Sample (NIS) from 2017–2020. Patients were stratified into four comorbidity groups: COPD alone, ILD alone, both COPD and ILD, and neither condition (reference). Covariates included sociodemographic factors (age, sex, race, income), comorbidity burden (Charlson Comorbidity Index), and hospital characteristics (teaching status, region). A year 2020 indicator was included to account for potential COVID-19 effects. Multivariable logistic regression estimated adjusted odds ratios (aORs) for inpatient mortality. Missing or invalid data for key variables were excluded. Results: Of 2,640 hospitalizations for lung cancer patients with RP, 301 (11.4%) resulted in inpatient death. The mean age was 70.8 years (SD 9.6), with 43.2% females (n = 1,141) and 56.8% males (n = 1,499). The racial distribution was predominantly White (81.0%), followed by Black (10.8%), Hispanic (3.67%), Asian (2.27%), and other races (2.23%). Patients with both ILD and COPD had the highest mortality risk (aOR 2.00, 95% CI 1.20–3.25, p = 0.006), while COPD alone was associated with reduced mortality (aOR 0.59, 95% CI 0.45–0.77, p < 0.001). ILD alone was not a significant predictor (aOR 1.33, 95% CI 0.78–2.17, p = 0.273). Higher Charlson Comorbidity Index scores were independently associated with greater mortality risk (aOR 1.07, 95% CI 1.01–1.12, p = 0.012). Female sex was protective (aOR 0.74, 95% CI 0.57–0.95, p = 0.019). Other factors, including age, race, income, and hospital characteristics, were not significant predictors. Conclusions: Patients with both ILD and COPD had significantly elevated mortality risk, while ILD alone did not. Unexpectedly, COPD alone appeared protective against mortality. These findings highlight the need for further research into the biological and clinical mechanisms underlying these relationships, including the role of inflammatory pathways and lung dynamics. A better understanding of these factors could inform personalized management strategies to improve outcomes in this high-risk population.