Human Microbiome as Clinical Biomarkers for Respiratory Tract Cancers

Respiratory tract cancers (RTCs), including lung, laryngeal, nasopharyngeal, and tracheal cancers, are among the most common cancer types. These cancers show difficulties in the case of early diagnosis and treatment monitoring. The microbiome, the community of microbes living in a single area of the body, is associated with cancer and offers potential for developing non-invasive diagnostic tools and probiotic therapies. Microbiome dysbiosis affects both the tumor and the immune microenvironment. The major pathways of RTCs, including EGFR, ALK, KRAS, STAT3, WNT, etc., are affected by the dysbiosis that occurs during cancer progression. Several microbial species have also been associated with treatment outcomes of immune checkpoint inhibitors (ICIs), chemotherapy, and anti-PD-1 therapy. Microbes such as Alistipes indistinctus, Alistipes shahii, Barnesiella viscericola, Streptococcus salivarius, Parabacteroides, and Faecalibacterium, along with genera like Bifidobacterium, Collinsella, Veillonella, and families/orders like Actinomycetales, Odoribacteraceae, and Selenomonadales, have shown positive associations with overall survival, progression-free survival, and improved treatment responses. Conventional biomarkers for RTCs have greatly improved diagnosis and monitoring. Still, they suffer from limitations such as low sensitivity in early-stage, intrusive sample procedures, and a lack of specificity. In contrast, gut, airway, and oral microbiota have emerged as promising non-invasive biomarkers with established associations to cancer progression, metabolic pathways, immune responses, and treatment monitoring. Moreover, non-invasive sampling methods like stool, sputum, and oral swabs offer improved patient comfort and early detection opportunities. In this mini review, we explore global research on human microbiomes as potential diagnostic or therapeutic biomarkers and their associations with RTCs.