Stability of gut microbiota in non-small cell lung cancer patients during chemoradiotherapy and its association with radiation pneumonitis

To assess the intra-patient stability of gut microbiota across longitudinal samples in non-small cell lung cancer (NSCLC) patients treated with chemoradiotherapy (CCRT), its association with radiation pneumonitis (RP), and the factors driving such stability. Intra-patient gut microbial stability between consecutive time points was quantified by stability coefficients (mS scores) using iteratively growing-partitioned clustering. Patients with G0 RP exhibited higher mS scores compared with those with G2+ RP. LEfSe analysis of probiotic microbes revealed enrichment of <i>Faecalibacterium</i> (<i>p</i> = 0.030) and <i>Stenotrophomonas</i> (<i>p</i> = 0.045) in the high-stability group. The baseline abundance of <i>Faecalibacterium</i> (<i>p</i> = 0.040) was identified as an independent predictor of microbial stability during CCRT. Higher gut microbiota stability was associated with lower risk of RP in NSCLC. The composition of probiotics may contribute to the preservation of gut microbiota stability, and serve as a potential target to mitigate RP.