Cancers attributable to infectious agents in Nigeria

Abstract

Background:
Infections by certain viruses, bacteria, and parasites have been identified as risk factors for some cancers. In 2008, there were 12.7 million new cancer cases worldwide. About 2 million of these new cases were attributable to infections, which represent 16.1% of new cancer cases. The majority of these cancers occurred in less-developed regions of the world, where the Population Attributable Fraction (PAF) was estimated to be 23%. We carried out this study to evaluate the numbers of cancers in Nigeria from 2012-2014 that are attributable to infections using data from Population Based Cancer Registries (PBCR) in Nigeria.

Methods:
We considered cancers associated with Epstein-Barr virus (EBV), Human Papilloma Virus (HPV), Hepatitis B and C Virus (HBV/HCV), Human Immunodeficiency Virus and Human Herpes Virus 8 (HIV/HHV8), Helicobacter pylori, and Schistosoma haematobium that have been classified as oncogenic by IARC. We obtained data on the infection-associated cancers from registry databases of 3 PBCRs in Nigeria: Abuja, Enugu, and Calabar cancer registries. We used PAF for infectious agents associated cancers in developing countries, which were calculated using prevalence data and relative risk estimates in previous studies: EBV and Nasopharyngeal (90%), and Hodgkin's Lymphoma (80%); HPV and Cervical (100%), Vulval and Vaginal (40%), Anal (90%) and Oropharyngeal cancer (12%) in women; Penile (40%), Anal (90%) and Oropharyngeal cancer (12%) in men; HBV/HCV and Liver (92%), HIV/HHV8 and Kaposi sarcoma (100%), Non Hodgkin Lymphoma (100%); H. pylori and stomach (74%) and S. haematobium and Bladder cancer (56.6%).
Results:
The 3 PBCRs reported 4,861 cancer cases from 2012-2014: 1,875 male cases and 2,986 female cases. There were 412 infection-associated cancers in males accounting for 22% of total cancers in males, and 351 (85%) of these were attributable to infections. In females, there were 727 infection-associated cancers accounting for 24% of total cancers in females, and 674 (93%) of these were attributable to infections. Cancers of the Cervix (n=430), Liver (n=152), and Non-Hodgkin's Lymphoma (n=129) were the most common infection-associated cancers in both sexes. The most common infectious agents associated with cancers were HPV (n=453), HIV/HHV8 (n=199), HBV/HCV (n=143) and EBV (n=125).
Conclusion:
Our findings suggest that 85% of infection-associated cancers in males and 93% infection-associated cancers in females in Nigeria can be prevented with vaccination, safer risk behaviors, or anti-infective treatments.