# Prognostic Impact of Infectious Agents After Definitive Treatment in Non-Small Cell Lung Cancer

## TL;DR

Infections after lung cancer treatment are common and linked to worse survival, especially those caused by healthcare-associated bacteria.

## Contribution

This study identifies infections as a strong prognostic factor in NSCLC patients post-treatment.

## Key findings

- Infections within the first year after treatment were frequent and mainly caused by Gram-negative bacteria.
- Culture positivity was an independent predictor of worse overall survival in NSCLC patients.
- Healthcare-associated infections were prevalent and associated with poorer outcomes.

## Abstract

Infections are common after definitive treatment in patients with non-small cell lung cancer (NSCLC), but their prognostic significance has not been clearly established. In this retrospective study, 214 patients with NSCLC who underwent definitive treatment were evaluated. Infections were found to be frequent within the first year after treatment, mainly caused by Gram-negative bacteria such as Pseudomonas aeruginosa and Acinetobacter baumannii. A substantial proportion of the isolated pathogens were healthcare-associated. Patients with positive cultures had significantly shorter overall survival. These findings demonstrate that infections are a strong prognostic factor in NSCLC after definitive treatment. Early microbiological evaluation, appropriate therapy, and strict infection prevention strategies are critical to improving overall survival in this vulnerable group.

Background: Infections are common complications in patients with non-small cell lung cancer (NSCLC) and may adversely influence clinical outcomes. Their prognostic impact after definitive treatment is not well established. This study aimed to investigate the incidence, microbiological profile, and prognostic significance of infections occurring within one year after definitive treatment in patients with NSCLC. Methods: We retrospectively analyzed patients with NSCLC who completed definitive treatment between 1 January 2016, and 31 December 2023. Microbiological culture results obtained within one-year post-treatment and inflammatory markers measured one month after treatment were evaluated. Pathogens were classified as healthcare-associated infection (HAI) or non-HAI agents. Overall survival (OS) was estimated using the Kaplan–Meier method, and prognostic factors were assessed using Cox regression analysis. Results: Among 214 eligible patients, 45 had positive microbiological cultures. Gram-negative bacteria predominated (n = 24), with Pseudomonas aeruginosa (n = 8) and Acinetobacter baumannii (n = 6) being the most frequently isolated species. Among all isolates, 20 Gram-negative and 6 Gram-positive microorganisms were identified as HAI pathogens. In multivariate analysis, culture positivity (HR: 2.75, p < 0.001) remained an independent prognostic factor for worse OS. Conclusion: Infections within the first year after definitive treatment, particularly those caused by HAI-related Gram-negative pathogens, are associated with reduced OS in NSCLC. Early microbiological diagnosis, targeted antimicrobial therapy, and strict infection prevention strategies may help improve outcomes in this high-risk population.