Bacterial Lipopolysaccharide as a Negative Predictor of Adjuvant Gemcitabine Efficacy in Pancreatic Cancer.

Adjuvant gemcitabine (aGC) is one standard of care after pancreatic ductal adenocarcinoma (PDAC) resection. No biomarker for its efficacy is established. As bacteria mediate gemcitabine resistance, we analyzed whether lipopolysaccharide (LPS) as surrogate for bacterial colonization is prognostic in PDAC patients treated with aGC or without aGC adjuvant gemcitabine. We detected LPS in 86 tumors from 376 patients, which defined a specific microbiome as revealed by 16 s-rRNA-sequencing. In the 230 aGC patients, LPS conferred worse disease-free survival (8.3 vs 13.7 months; hazard ratio = 1.75, 95% confidence interval = 1.22 to 2.49; log-rank P = .002) and overall survival (21.7 vs 28.5 months; hazard ratio = 1.80, 95% confidence interval = 1.23 to 2.57; log-rank P = .001) but not in the 146 naGC patients, which was confirmed in an independent validation cohort (n = 178). LPS may serve as a negative predictor for aGC efficacy in PDAC, which suggests a role for microbiome modification to overcome bacteria-mediated chemotherapy resistance.