Association of Intratumoral Bacterial Abundance With Lung Cancer Prognosis in Chiba University Hospital Cohort

The relationship between cancer prognosis and intratumoral microbiome has recently gained attention. Regarding lung cancer, most studies have focused on bacteria outside tumors, such as sputum or lavage fluid, with few examining intratumoral bacteria and their impact on prognosis. In this study, we extracted DNA from lung tumor samples of 507 patients undergoing surgery at Chiba University Hospital and quantified intratumoral bacterial abundance using bacteria-specific PCR primers. Bacteria were detected in 77.1% of cases, and bacterial abundance was significantly higher in lung adenocarcinoma than in squamous cell carcinoma. Patients were categorized into three groups (High, Low, and Very-Low) based on bacterial abundance, and associations with clinicopathological factors were analyzed. In lung squamous cell carcinoma, higher bacterial abundance was significantly associated with worse recurrent-free survival and overall survival and was found to be a poor prognostic factor independent of pathological tumor stage. In conclusion, intratumoral bacterial abundance was found in the majority of lung cancer tissues, with variations based on pathology. This abundance may serve as a useful marker for stratifying lung squamous cell carcinoma with distinct prognoses.