Gut microbiota and association with clinical response to anti-PD-1 based immunotherapy combined with chemotherapy in Chinese patients with lung cancer.

e21005 Background: The gut microbiome has been demonstrated to be closely related to not only the occurrence of lung cancer but also its anti-PD-1 based immunotherapy and chemotherapy. There is little characteristic analysis of gut microbiota in Chinese lung cancer patients, and the impact of gut microbiota on combined anti-PD-1 treatment and chemotherapy remains unclear. Methods: Fecal samples from 22 healthy volunteers and advanced-NSCLC 21 patients who were treated in the Fourth Hospital of Hebei Medical University from 2019 to 2021 before and after anti-PD-1 treatment combined with chemotherapy were collected. DNA was extracted from all samples, and the V3-V4 region of the bacterial 16S rRNA gene was PCR-amplified using the Illumina sequencing platform. The study results were analyzed using bioinformatic data. Results: The composition of gut microbes in NSCLC patients and healthy people at the phylum level was roughly similar, with Firmicutes as the main phylum. However, there were significant differences in Beta diversity (P<0.05). The bray_curtis principal coordinate analysis revealed a significant difference in the microbiota between patients before and after combined treatment (P<0.05). According to the RECIST 1.1 criteria, the efficacy of the combination therapy was evaluated. The patients with complete remission, partial remission, or stable efficacy after 6 cycles were the clinical benefit response group (CBR, n=10), and the patients with disease progression in the efficacy evaluation were the non-clinical benefit group (NCB, n=8). The results suggested that the CBR group was enriched in Bifidobacterium_longum, Bifidobacterium_adolescentis, Bifidobacterium_bifidum, and Bifidobacterium_breve at the species level (P<0.05) compared with the NCB group. Compared with the median progression-free survival (mPFS) of patients without Bifidobacterium_breve at baseline, the mPFS of patients with the kind of gut bacteria was significantly prolonged (P<0.001).Specifically, mPFS without Bifidobacterium_breve group was 106 days (95% CI: 37-175), mPFS of the Bifidobacterium_breve group was Not Reached (95% CI: NC-NC). Conclusions: The clinical response of combined anti-PD-1 treatment and chemotherapy in advanced NSCLC patients was closely associated with the gut microbiome,and Bifidobacterium_breve may be effective biomarkers to predict the survival benefit of NSCLC combined therapy, which provided new therapeutic targets for modulating the response to cancer therapy.