Uncovering Linkages between HIV and Cancer in South Africa
It is estimated that about 36.7 million people are currently living with HIV/AIDS around the world. The global health community has spread awareness on preventative measures, testing, and treatment options, but what many people don’t know is that HIV is actually a carcinogen — capable of causing cancer. While the impact of HIV/AIDS is well documented, cancer is sometimes overlooked in the public as an emerging and deadly health issue among low-to middle-income countries. In 2008, 715,000 new cancer cases and 542,000 cancer deaths occurred in Africa. Experts expect these numbers to triple by 2030.
Spearheaded by the U.S. National Institutes of Health’s National Cancer Institute (NCI), the African Organisation for Research and Training in Cancer (AORTIC), and implemented by CRDF Global, the Beginning Investigator Grant for Catalytic Research (BIG CAT) program was started to shed light on the impact of cancer in Africa. Through grant management and professional development training, CRDF Global partnered with NCI and AORTIC to build the of capacity of young investigators in Sub-Saharan Africa working on cancer research. Dr. Mazvita Sengayi, senior epidemiologist at the National Health Laboratory Service in South Africa was awarded a grant to explore the burden of cancers attributable to HIV at a national level.
Read about Dr. Sengayi’s work below.
Growing up, did you always want to become a scientist? What encouraged you to pursue a career in research and public health?
MS: I grew up in a small town in the north western part of Zimbabwe. Due to limited exposure, I didn’t know much about science or research careers. My mother worked as a nurse at the local hospital and she ignited a love of medicine in me. I went on to study medicine at the University of Zimbabwe, graduating in 2002 at the peak of the HIV epidemic in Zimbabwe. It was a difficult time to practice medicine with high patient mortality due to lack of antiretroviral treatment in a high HIV prevalence setting. I knew that the symptomatic care we were giving HIV positive patients at that time was inadequate and ineffective and new drugs (antiretroviral drugs) and new ways of management were needed for the HIV crisis. I went on to study a postgraduate diploma in HIV management at the College of Medicine of South Africa to equip myself better in the management of HIV positive patients who were now the bulk of the patients I was seeing. It was at this time that I got interested in research and in epidemiology and I joined a pediatric HIV clinical trial team. (I enjoy epidemiology a lot because it is a “big picture” science and it combines health science with mathematics, the two things I have always loved.
What type of research do you work on at the National Health Laboratory Services.
MS: I work for the National Cancer Registry (NCR), which is a department within the National Institute of Communicable Diseases (NICD) division of the NHLS. Our primary role is national cancer surveillance in South Africa through a pathology-based cancer registry. We are also in the process of establishing a population-based cancer registry in Ekurhuleni District, Gauteng province. The South African HIV Cancer Match study (SAM) is our flagship study at the NCR. The SAM study is a probabilistic record linkage study of a national HIV cohort created from HIV laboratory data (CD4 counts, viral load, HIV tests) linked to NCR data in order to study spectrum and incidence of cancer in HIV-positive people at national level. The study is a collaboration between the NCR and the Institute for Social and Preventive Medicine, University of Bern, Switzerland. I also work on the Johannesburg Cancer case-control study, which explores risk factors for cancer in adult black Africans in Johannesburg.
The HIV epidemic in South Africa has been largely documented and covered over the years, yet the prevalence of cancer is much less discussed. Is cancer a growing health issue in South Africa? Which cancers are most prevalent? The NCR is a pathology-based cancer registry, meaning that while it is highly specific, it has low sensitivity missing cancers that are not laboratory diagnosed, hence the need to establish a population-based cancer registry. Recent increases in cancer incidence are mainly due to improved reporting after legislation was passed which made cancer a reportable disease in 2011. The five most prevalent cancers in 2012 in women are breast, cervical, colorectal, uterus and lung cancer. In men, there were prostate, lung, colorectal, oesophagus and bladder cancer. The data are available on the NCR website. The high HIV prevalence has resulted in changes in national cancer patterns with previously rare cancers like Kaposi’s sarcoma emerging in the top ten most common cancers in the country.
What does your current project with CRDF Global focus on?
MS: South Africa has about 6.8 million HIV-positive people, making it the country with the largest number of people living with HIV in the world. HIV is known to be one of the viruses that can cause cancer. Currently, it is not known to what extent the huge HIV burden in South Africa has affected the occurrence of cancers in the general population. There are several unanswered questions. Which types of cancer occur in HIV-positive people in South Africa and how do these differ from those occurring in people without HIV? How much is HIV contributing to overall cancers in South Africa? Have there been any changes in cancer trends since antiretroviral treatment (ART) became available in South Africa? To answer these questions, we will link databases of laboratory HIV tests to cancer cases, so that we can know the HIV status of cancer patients recorded in the South African National Cancer Registry. This will allow us to estimate the contribution of HIV to cancer in South Africa, the type of cancers that occur in HIV-positive people, the additional risk of cancer that HIV-positive people have compared to people who do not have HIV and changes in cancer trends since antiretroviral drugs became available (2004 – 2014). This information is crucial for national planning, development of strategies to reduce cancers as well as cancer resource allocation in South Africa where we have many people living with HIV, who are now living to older ages because of antiretroviral treatment.
How will this research grant help further your work?
MS:The CDRF Global BIG CAT grant funds a sub-study within the SAM study entitled “Burden of cancers attributable to HIV in South Africa 2004 - 2014”. This study explores the additional risk that HIV positive people face in comparison with the general population and the burden of cancers attributable to HIV at national level. While we have studied incidence of cancer in HIV positive South Africans on ART, the additional risk that HIV positive South Africans face compared to HIV- negative people is not known particularly in the context of ART availability in South Africa. This grant allowed me to be a first-time principal investigator, which will be useful for reference when applying for funding for future work. The grant has also allowed for further strengthening of our collaboration with University of Bern, while building local cancer epidemiology capacity through supporting an MSc Epidemiology student.
Why is it important to study any potential links between HIV and cancer?
MS: HIV was classified as a carcinogen (cancer-causing agent) in 1996 by the International Agency for Research in Cancer (IARC). While a lot of work has been done on HIV-related cancers in developed nations (see studies below), there is still very little data on cancer risk in HIV infected African populations in the context of ART availability. HIV populations in Africa are very different (majority are female, low smoking prevalence, have mostly heterosexual transmission, mostly HIV 1 subtype C, ART only available since 2004) from HIV populations in Europe and the US (mostly male, intravenous drug use and MSM are important modes of transmission, high smoking prevalence, mostly HIV 1 subtype B, ART available since 1996). This necessitates exploration of cancer patterns in African populations. South Africa has the largest number of people living with HIV in a single country, and this allows enough power to explore cancer risk in the HIV population. Cancer has become an important cause of death as competing causes of mortality(such as opportunistic infections) become less with improved immunity when patients have access to ART. HIV impairs the immune system allowing cancers to occur at much younger ages than in the uninfected persons, thus creating an “experiment of nature”, which may have implications for understanding more about cancers in general. For all these reasons, the importance of exploring links between HIV and cancer cannot be overstated.
What is the most challenging about your work?
MS: One of the biggest challenges is getting funding for research projects since our research team, while enthusiastic and knowledgeable about the local health issues, is small and young.
What is most rewarding?
MS: The most rewarding part of my work is creating new knowledge in cancer epidemiology which can be used to inform cancer control policy in South Africa. My work allows the use routinely collected health data to inform health policy, ultimately helping to improve health outcomes of the same population that contributed the data.
Additional reading on HIV-related cancers in developed nations
- Dal Maso L, Polesel J, Serraino D, Lise M, Piselli P, Falcini F, et al. Pattern of cancer risk in persons with AIDS in Italy in the HAART era. Br J Cancer [Internet]. 2009 Mar 10 [cited 2012 Jun 18];100(5):840–7. Available from: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2653754&tool=p...
- Silverberg MJ, Chao C, Leyden W a, Xu L, Tang B, Horberg M a, et al. HIV infection and the risk of cancers with and without a known infectious cause. AIDS [Internet]. 2009 Nov 13 [cited 2012 Jun 18];23(17):2337–45. Available from: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2863991&tool=p...
- Shiels MS, Pfeiffer RM, Gail MH, Hall HI, Li J, Chaturvedi AK, et al. Cancer burden in the HIV-infected population in the United States. J Natl Cancer Inst [Internet]. 2011 May 4 [cited 2012 Apr 14];103(9):753–62. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21483021
- Clifford GM, Polesel J, Rickenbach M, Dal Maso L, Keiser O, Kofler A, et al. Cancer risk in the Swiss HIV Cohort Study: associations with immunodeficiency, smoking, and highly active antiretroviral therapy. J Natl Cancer Inst [Internet]. 2005 Mar 16 [cited 2012 Mar 11];97(6):425–32. Available from: http://www.ncbi.nlm.nih.gov/pubmed/15770006