This study investigates the impact of gut microbiota on the effectiveness of immunotherapy in patients with advanced non-small cell lung cancer (NSCLC). The researchers analyzed 16S ribosomal RNA (rRNA) and gas chromatography-mass spectrometry (GC–MS) sequencing data from 71 stool samples of NSCLC patients before treatment with immune checkpoint blockade (ICB). They found a significant association between elevated gut microbiota diversity and better response to ICI treatment, with Faecalibacterium being significantly increased in responders (R) compared to nonresponders (NR). Faecalibacterium production of short-chain fatty acids (SCFAs), particularly butanoic, acetic, and hexanoic acids, was also higher in R patients. Fecal microbiota transplantation (FMT) from R and NR patients into mice with Lewis lung cancer cells showed that FMT from R patients promoted an anticancer effect and reduced Ki-67-positive cells in tumors, while FMT from NR patients did not significantly alter PD-L1 expression. The study concludes that gut microbiota diversity and SCFAs are related to the efficacy of immunotherapy in NSCLC, and FMT can effectively delay tumor progression and enhance immunotherapy effects.This study investigates the impact of gut microbiota on the effectiveness of immunotherapy in patients with advanced non-small cell lung cancer (NSCLC). The researchers analyzed 16S ribosomal RNA (rRNA) and gas chromatography-mass spectrometry (GC–MS) sequencing data from 71 stool samples of NSCLC patients before treatment with immune checkpoint blockade (ICB). They found a significant association between elevated gut microbiota diversity and better response to ICI treatment, with Faecalibacterium being significantly increased in responders (R) compared to nonresponders (NR). Faecalibacterium production of short-chain fatty acids (SCFAs), particularly butanoic, acetic, and hexanoic acids, was also higher in R patients. Fecal microbiota transplantation (FMT) from R and NR patients into mice with Lewis lung cancer cells showed that FMT from R patients promoted an anticancer effect and reduced Ki-67-positive cells in tumors, while FMT from NR patients did not significantly alter PD-L1 expression. The study concludes that gut microbiota diversity and SCFAs are related to the efficacy of immunotherapy in NSCLC, and FMT can effectively delay tumor progression and enhance immunotherapy effects.