Secondary infections after diagnosis of severe radiation pneumonitis (SRP) among non-small cell lung cancer patients: pathogen distributions, choice of empirical antibiotics and the value of empirical antifungal treatment.

Abstract

OBJECTIVES\nTo assess pathogen distributions and antimicrobial sensitivity characteristics in non-small cell lung cancer (NSCLC) patients diagnosed with severe radiation pneumonitis with secondary infections.\n\n\nMETHODS\nData from 1746 NSCLC patients diagnosed with severe radiation pneumonitis following thoracic radiotherapy from January 2009 - December 2020 were retrospectively analyzed. Pneumonia incidence, causative pathogens, and antibiotic resistance characteristics in secondary lung infections patients were analyzed. Risk factors associated with mortality were identified through univariate and multivariate analyses. Antifungal drug efficacy and duration-related effects were assessed with Forest plots and ROC curves.\n\n\nRESULTS\nOverall, 44.5% (777/1746) NSCLC patients with severe radiation pneumonitis were diagnosed with secondary lung infections. In total, 899 bacterial strains were isolated from these patients, with Acinetobacter baumannii (206/899, 27%), Klebsiella pneumonia (200/899, 26.2%), and Pseudomonas aeruginosa (104/899, 13.6%) being most common. Carbapenems and cefoperazone-sulbactam resistance rates of 52.7%/32.2%, 28.8%/26.4%, and 23.7%/20.2% were observed for these isolates, respectively. Infection-related deaths occurred in 22.4% severe radiation pneumonitis patients. Independent risk factors for infection-related death included poor performance status (PS) scores, inappropriate empirical antimicrobial treatment, bacteria/fungal co-infection, and lack of empirical antifungal treatment. ROC curves showed the cut-off value of empirical antifungal treatment duration was 9 (AUC=0.819).\n\n\nCONCLUSION\nFor severe radiation pneumonitis patients with secondary lung infections, appropriate empirical antimicrobial treatment could decrease infection-related mortality, and cefoperazone-sulbactam may be an appropriate antibacterial drug. Empirical antifungal treatment for a minimum of 9 days might contribute to better outcomes. While this represents a promising treatment approach for severe radiation pneumonitis patients with secondary lung infections prior to antibacterial susceptibility testing, further prospective validation is essential.