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]. The gene discussed is PDCD1; the disease is colorectal carcinoma.