Association between Echinococcus granulosus infection and cancer risk – a pilot study in Cyprus

Background: Infections from microorganisms and parasites have been connected with either increased or decreased cancer risk. The objective of this study was to investigate whether infection by Echinococcus granulosus is associated with cancer risk. Methods: We assembled a pilot retrospective cohort of patients who were diagnosed as being infected by E. granulosus in Cyprus between 1930 and 2011. Age/gender-matched non-infected family members and neighbors were selected as references. Medical history was ascertained from each study subject through in-person interview. Cox proportional hazards regression analysis was performed to assess the association of being infected by E. granulosus with cancer risk. Results: Individuals with prior infection by E. granulosus (n=249) were more likely to have cancer compared to those without infection (n=753), 11.65% vs. 8.37% (p=0.0492). Survival analysis also showed that subjects with prior infection had a higher risk for developing cancer. The hazards ratio (HR) was 1.595, [95% confidence interval (CI) between 1.008 and 2.525]. The risk ratio did not change significantly (HR=1.536; 95% CI: 0.965–2.445) after adjusting for gender, year of birth, smoking status, alcohol consumption, and family history of cancer. Conclusions: Our study suggests that infection by E. granulosus may increase cancer risk. If this observation can be confirmed independently, further investigation of the mechanisms underlying the association is warranted.