Severe Salmonella spp. or Campylobacter spp. Infection and the Risk of Biliary Tract Cancer: A Population-Based Study

SIMPLE SUMMARY: Although it is known that bacterial infection may increase risk of cancer, the relationship between certain infections and cancer remains ill-quantified. To identify potential risk factors, this study compared the incidence of biliary tract cancer (BTC) in patients with Salmonella spp. or Campylobacter spp. infection to the general population in a large Western cohort of 16,252 salmonellosis and 27,668 campylobacteriosis patients. Standardized relative incidence ratio for BTC was 1.53 (95% CI 0.70–2.91) in salmonellosis patients and 0.97 (95% CI 0.39–2.00) in campylobacteriosis patients. Patients with Salmonella spp. infection and BTC were significantly younger than BTC patients without Salmonella spp. infection. Potentially, the study was underpowered to detect differences in cancer incidence, or cancer etiology in Western patients differs from those in non-Western countries and instead of bacterial infection, other factors contribute to cancer risk. Better understanding of cancer etiology is needed to identify risk factors and facilitate screening and early detection of cancer patients. ABSTRACT: Salmonella spp. infection has shown to have oncogenic transformative effects and thereby increases the risk of certain cancers. For Campylobacter spp., similar effects have been demonstrated. Risk factor identification may allow for timely diagnosis and preventive treatment. To substantiate the oncogenic potential of Salmonella and Campylobacter spp., this study compared the incidence of extrahepatic biliary tract cancer (BTC) in patients with diagnosed Salmonella or Campylobacter spp. infection with BTC incidence in the Netherlands. National infectious diseases surveillance records of patients diagnosed with a laboratory-confirmed Salmonella or Campylobacter spp. infection during 1999–2016 were linked to the Netherlands Cancer Registry. Incidence of BTC in Salmonella and Campylobacter spp. patients was compared to the incidence of BTC in the general population using Standardized Incidence Ratios (SIRs). In total, 16,252 patients were diagnosed with Salmonella spp. and 27,668 with Campylobacter spp. infection. Nine patients developed BTC at a median of 46 months (13–67) after Salmonella spp. infection and seven at a median of 60 months (18–138) after Campylobacter spp. infection. SIR of BTC in salmonellosis patients was 1.53 (95% CI 0.70–2.91). In patients aged <60 years, the SIR was 1.74 (95% CI 0.36–5.04). For campylobacteriosis patients, the SIR was 0.97 (95% CI 0.39–2.00). Even though Salmonella or Campylobacter spp. infection was not significantly associated with increased BTC risk in this cohort, it remains extremely important to study potential risk factors for cancer to facilitate screening and ultimately improve prognosis of cancer patients.