Clinical significance of microbial colonization identified by initial bronchoscopy in patients with lung cancer requiring chemotherapy

Background There are limited data on the association between bronchial colonization and respiratory infections in people with lung cancer requiring cytotoxic chemotherapy. We investigated whether bronchial colonization in initial bronchoscopy specimens can predict the development of pneumonia after chemotherapy in patients with lung cancer. Methods Four hundred thirteen patients with lung cancer included in the Catholic Medical Center lung cancer registry were enrolled from March 2015 to August 2018. Demographic data, microbiology results, development of pneumonia after chemotherapy, and clinical information about lung cancer were analyzed retrospectively. Results A total of 206 lung cancer patients treated with chemotherapy were included in the analysis. Forty patients (19.4%) had positive results for the bronchial washing culture during the initial evaluation of lung cancer. The most common organisms were Klebsiella pneumoniae (n=14) and Streptococcus pneumoniae (n=6) in the surveillance culture, and Pneumocystis jirovecii (n=12) and Staphylococcus aureus (n=8) at the time of pneumonia development. Eighty-nine patients (43.2%) had pneumonia after chemotherapy, but the occurrence of pneumonia did not differ according to the colonization. There were no patients for whom the initial isolated organism was a causative microbe for the development of pneumonia after or during chemotherapy. The pneumonia group had poorer prognosis than the non-pneumonia group (378 vs. 705 days, P=0.0004). Conclusions Microbial colonization in bronchoscopy specimens was not associated with pneumonia development or mortality after chemotherapy for lung cancer. This finding suggests that testing surveillance culture may not be helpful for predicting pneumonia or improving survival in lung cancer patients with chemotherapy.