Grant: Travel Awards - Institute Community Support

Multiple infectious viruses and bacteria, such as Helicobacter pylori, hepatitis B and C, and human papillomavirus (HPV) are established risk factors for certain cancers. Eleven infections are responsible for approximately one-sixth of global cancer cases. Cancers caused by infections are generally preventable with vaccines or antibiotics. To improve our understanding of the burden of cancers due to modifiable risk factors, we estimated the proportion of cancers diagnosed among Canadians aged 18 and older in 2012 that were related to infections. To do this, we systematically reviewed the literature to collect relevant data for calculating population attributable fractions (PAFs). A PAF quantifies the possible reduction in new cancer cases that could be achieved if the infection were eliminated. PAFs were calculated for 19 cancer sites linked to infections, and for an additional nine cancer sites where the relationship between the infection and cancer was more recently discovered. We found that the seven infections with exposure in Canada, Epstein-Barr virus (EBV), hepatitis B and C, Helicobacter pylori, human herpesvirus 8 (HHV-8), human T-cell lymphotropic type 1 (HTLV-1), and human papillomavirus (HPV), were responsible for approximately 6,000 cancer cases representing 3.4% of cancers diagnosed in 2012 in Canada. Among these cancer cases due to infections, 54% were related to HPV, 28% to Helicobacter pylori, 9% to hepatitis B and C, 8% to EBV and the remaining 1% to HHV-8 and HTLV-1. The analysis of newer associations will include hepatitis B and C in bile duct cancer, EBV in stomach cancer, Helicobacter pylori in colorectal cancer, HPV in laryngeal cancer, among others. The current PAF of 3.4% will increase when we include the results of the additional nine infection-cancer site associations. The study findings will assist Canadian public health decision makers in prioritizing interventions that decrease the number of cancers associated with infections.