ObjectiveTo characterise the gut microbiome in subjects with and without polyps and evaluate the potential of the microbiome as a non-invasive biomarker to screen for risk of colorectal cancer (CRC).DesignPresurgery rectal swab, home collected stool, and sigmoid biopsy samples were obtained from 231 subjects undergoing screening or surveillance colonoscopy. 16S rRNA analysis was performed on 552 samples (231 rectal swab, 183 stool, 138 biopsy) and operational taxonomic units (OTU) were identified using UPARSE. Non-parametric statistical methods were used to identify OTUs that were significantly different between subjects with and without polyps. These informative OTUs were then used to build classifiers to predict the presence of polyps using advanced machine learning models.ResultsWe obtained clinical data on 218 subjects (87 females, 131 males) of which 193 were White, 21 African-American, and 4 Asian-American. Colonoscopy detected polyps in 56% of subjects. Modelling of the non-invasive home stool samples resulted in a classification accuracy >75% for Naïve Bayes and Neural Network models using informative OTUs. A naïve holdout analysis performed on home stool samples resulted in an average false negative rate of 11.5% for the Naïve Bayes and Neural Network models, which was reduced to 5% when the two models were combined.ConclusionGut microbiome analysis combined with advanced machine learning represents a promising approach to screen patients for the presence of polyps, with the potential to optimise the use of colonoscopy, reduce morbidity and mortality associated with CRC, and reduce associated healthcare costs.

Background. Gastric carcinoids are uncommon, and are unlike carcinoids at other gastrointestinal sites, clinically and pathologically. Methods. The authors studied specimens from 104 patients with gastric carcinoid, with study emphasis being placed on pathologic features, immunohistochemistry, clinical associations, and prognostic factors. Results. The average age of the 47 male patients and 57 female patients was 61 years. Twenty‐seven patients had chronic atrophic gastritis, 12 had pernicious anemia, and 6 had hypergastrinemia; no patient had carcinoid syndrome. Most of the tumors were confined to the mucosa and submucosa. Lymph node metastases were present in only one patient. The tumors were argyrophilic in 84% and argentaffin in 14%. Chromogranin tested positive in all patients; serotonin was detected in one‐third; other hormones were much less common. Gastrin‐positive tumors were antral. Of the 62 patients with follow‐up, 44 were alive without disease, 4 were alive with disease, and 14 were dead (4 died of carcinoid‐related disease). None of the deceased had pernicious anemia or hypergastrinemia. The tumors in patients with a fatal outcome were 2 cm or larger. Conclusion. Gastric carcinoids generally are indolent tumors, particularly when associated with pernicious anemia or hypergastrinemia or when smaller than 2 cm. Chromogranin is the most sensitive marker.

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