A growing body of evidence has associated the oral microbiome with gastric and oesophageal cancers. Micro-organisms such as Tannerella forsythia and Porphyromanos gingivalis are both organsims associated with these diagnoses and are typically associated with periodontal disease. The mechanism by which these organisms might cause cancer is undetermined, but is thought to be through a variety of pathways, such as the dehydrogenation of ethanol to acetaldehyde, resulting in DNA damage and mutation, as well as excessive proliferation of epithelium. Still, conclusions of these associations have historically been inconsistent due to variation in study design, exposure ascertainment and confounding adjustment. Recently published in the British Medical Journal, a large cohort, long-term follow-up prospective study has reported a clear association with periodontal disease and gastric and oesophageal cancer.
Enrolling 98, 459 women and 49,685 men, these patients were followed over 22-28 years, collecting dental history and cancer diagnoses. In total, 199 cases of oesophageal adenocarcinoma and 238 cases of gastric adenocarcinoma were reported. Having a history of periodontal disease was associated with a 43% and 52% increased risk of oesophageal adenocarcinoma (HR[95%CI]: 1.43[1.05-1.96], P= 0.02) and gastric adenocarcinoma (HR[95%CI]: 1.52[1.13-2.04], P= 0.006). Risk was also stratified by tooth loss, finding that compared to patients who had not lost any teeth, that patients who lost ≥2 teeth had an increased risk of 42% (HR[95%CI]: 1.42[1.00-2.03], P= 0.05) and 33% (HR[95%CI]: 1.33[0.95-1.86], P= 0.09), respectively. Furthermore, among patients with a history of periodontal disease, losing no teeth and losing ≥1 tooth were associated equally with the same increased risk of oesophageal cancer, at 59% (HR[95%CI]: 1.59[1.04-2.41], HR[95%CI]: 1.59[1.04-2.44], respectively). Conversely, these patients had different risks for gastric adenocarcinoma; patients with periodontal disease and no tooth loss had a risk of 50% (HR[95%CI]: 1.50[1.01-2.23]), whilst patients with ≥1 lost teeth had a risk of 68% (HR[95%CI]: 1.68[1.13-2.50]).
Although prospective research directly investigating the oral microbiome is still needed, these findings indicate oral microbiota as readily accessible, non-invasive biomarkers that may help identify patients at high risk.