[Gut Microbiota as a Potential Biomarker for Immune Checkpoint Inhibitors]

Immune checkpoint inhibitors(ICIs)currently play a predominant role in the standard treatment of non-small cell lung cancer(NSCLC)across all stages. While PD-L1 positivity has traditionally been used as the sole effective biomarker, evidence suggests that certain efficacy exists even in PD-L1-negative lung cancers. Various investigations have been conducted to identify biomarkers predicting the therapeutic efficacy of ICIs, focusing on both tumor-local and host-related factors. Among indicators reflecting the host status, the gut microbiota has garnered attention, with its composition and diversity potentially influencing the efficacy of ICI therapy. The presence of specific gut microbiota has been frequently reported to enhance the effectiveness of ICI treatment. Furthermore, the use of antibiotics may diminish the effects of ICIs, while fecal microbiota transplantation has shown potential to enhance ICI therapy. In our department, analysis of the gut microbiota in patients receiving anti-PD-1 antibody treatment has been conducted, yielding promising results through the identification of specific bacterial species and the search for these species using real-time PCR, suggesting avenues for further research. Recently, attention has also been drawn to the lung microbiota and tumor microbiota in the context of lung cancer, with reports suggesting that increased diversity in these microbial communities may correlate with the efficacy of ICI therapy. However, none of these findings alone provide sufficient evidence as standalone biomarkers, necessitating future research to advance from both the host environment, including the gut microbiota, and the microenvironment of the tumor site, such as the lung and tumor microbiota.