In-hospital outcomes of radiation pneumonitis and drug-induced pneumonitis in patients with breast cancer.

e23087 Background: Pneumonitis represents a significant adverse event among breast cancer patients undergoing advanced therapies, including immune checkpoint inhibitors and radiation therapy. However, data remain limited regarding the incidence of radiation pneumonitis (RP) and drug-induced pneumonitis (DP) in this population. Here, we study the incidence of RP and DP, their association with underlying chronic obstructive pulmonary disease (COPD) or smoking, and their impact on in-hospital outcomes. Methods: Data from the 2020 National Inpatient Sample (NIS) database, the largest inpatient care database in the United States was used. All the patients above 18 with a diagnosis of breast cancer were included, identified by ICD-10 codes. Patients with breast cancer diagnosis who developed RP and DP were similarly identified. Patients were grouped into 3 categories: no pneumonitis, patients with RP, and those with DP. Baseline demographics, including prevalence of COPD and smoking were obtained. Length of stay, total hospital charges, and death during hospitalization were analyzed between patients with breast cancer who developed pneumonitis compared to those without pneumonitis, and between patients with RP and DP, adjusting for baseline demographics. Sampling weights were applied to generate nationally representative sample. A 2-sided P < 0.05 was considered statistically significant. Results: A total of 160,140 study participants with breast cancer diagnosis were included. 485 (0.3%) had RP and 105 (0.1%) had DP. The study population was mostly females (98.7%), white (66.5%), had an income of $46,000-$58,000 (26.2%), and had Medicare insurance (54.8%). Overall, 29% had a smoking history, with a higher prevalence of smoking in patients with RP, which was not statistically significant ( RP- 29.9% vs DP- 23.9%, p-0.653). About 13% of the overall study population had COPD, with a statistically higher prevalence in patients with RP (RP- 14.4 % vs DP- 4.8%, p-0.048). The odds ratio of death was higher in patients with breast cancer who were diagnosed with pneumonitis compared to those without a diagnosis of pneumonitis (AOR- 2.0, 95% CI:1.03-3.91). The length of stay was also higher in patients with breast cancer who developed pneumonitis than those who did not (Adjusted Mean Difference: 1.8, 95% CI: 0.59 – 3.01). There was no difference in the total hospital charges for both groups. There were no significant differences in the odds of death, length of stay, and total hospital charges between RP and DP. Conclusions: Hospitalized breast cancer patients with pneumonitis experience poorer clinical outcomes, including higher mortality compared to those without pneumonitis. Patients with RP had a statistically higher prevalence of underlying COPD than DP. These findings underscore the need for careful monitoring and management of pneumonitis, particularly in patients with COPD, to improve outcomes.