Pathogen distribution characteristics and risk factors of pulmonary infection associated with immune checkpoint inhibitor therapy in patients with advanced non-small cell lung cancer: a case control study

BACKGROUND: To investigate the pathogen distribution and risk factors for pulmonary infection (PI) in patients with advanced non- small cell lung cancer (NSCLC) treated with chemotherapy combined with immune checkpoint inhibitors (ICIs). METHODS: Patients with advanced NSCLC who met the inclusion criteria were collected and divided into three groups: chemotherapy with PI group, chemotherapy combined with ICIs with PI group and chemotherapy combined with ICIs without PI group. We displayed the pathogen distribution and infection time of PI for different groups, and explored the risk factors for PI in chemotherapy combined with ICIs group of patients. RESULTS: A total of 239 patients were included in the study, among which there were 30 cases in the chemotherapy with PI group, 68 cases in the chemotherapy combined with ICIs with PI group, and 141 cases in the chemotherapy combined with ICIs without PI group. The results revealed an increased bacterial infection rate of patients in the chemotherapy with PI group (p = 0.003). Data analysis of patients with combined fungal infections showed a statistically significant difference in the incidence of fungal infections between the two groups (Fisher's exact test, p = 0.035). Multivariate logistic regression analysis revealed that low lymphocyte (LYM) counts (P = 0.016) and stage IV disease (P = 0.012) were independent risk factors for patients in the chemotherapy combined with ICIs with PI group, and number of immunotherapy cycles ≥ 5 (P = 0.031) was associated with a reduced likelihood of PI. CONCLUSIONS: In this observational study, bacterial infections were more common with chemotherapy alone, whereas fungal infections predominated in patients receiving chemotherapy plus ICIs. Low lymphocyte count and stage IV disease were associated with higher pulmonary infection risk, while ≥ 5 cycles of immunotherapy was associated with lower risk.