Specifically, for the first time, we identified that the genus Collinsella, genus Howardella, and genus Lachnospiraceae UCG008 increased and that the genus Peptococcus decreased in small intestine cancer patients, in spite of the reported associations between Collinsella and anti-PD-1 efficacy [47], between Collinsella and oesophageal adenocarcinoma [48], between Lachnospiraceae and anti-PD-1 efficacy [49], between Lachnospiraceae and CRC [37], and between Peptococcus and CRC [50]. This evidence concerns the gene PDCD1 and small intestine cancer.