Black men have a higher risk of prostate cancer than white men in South Africa

Prof Riana Bornman, Senior Research Professor at the University of Pretoria’s School of Health Systems and Public Health (SHSPH) and Prof Vanessa Hayes, a genomicist from the Garvan Medical Institute for Medical Research in Sydney, Australia, focused their research on prostate cancer in black Southern African men of Bantu and Khoisan descent, to better understand the possible links between prostate cancer and African ancestry.

Their study covered hospitals in Limpopo and Gauteng, where 99% of the participants were self-identified black African patients. These patients all had a more aggressive prostate cancer compared with similar studies conducted on European patients.

Previous research has shown that when compared with European Americans, African American men are 1.7 times more likely to develop prostate cancer and that they are generally younger (in their 40s and 50s) at diagnosis. Furthermore, they present with more aggressive disease characteristics, and consequently are also 2.5 times more likely of dying from the disease.

The current study included 837 men between 45 and 101, with a mean age of 70 years, who all had prostate disease. Of this group, 522 patients (62.4%) had prostate cancer. Black South African men presented with higher PSA levels and histopathological tumour grade compared with black Americans. This difference was further exacerbated in men from rural localities.

“The most common risk factors for prostate cancer include African ancestry, increasing age (from 50’s onwards) and a family history of prostate cancer – on either the maternal or paternal side,” said Prof Bornman. It might be that prostate cancer grows more rapidly in black than in white men and that transformation from latent to aggressive prostate cancer might occur earlier in black men.

“Because African ancestry is a risk factor, it means that for scientists to understand what leads to the development of prostate cancer, we have to investigate prostate cancer in African men – this means that African ancestry and aging will both be covered as risk factors,” she added.   

Previous studies have indicated that 61.8 per 100 000 men in southern Africa will develop prostate cancer. The lifetime risk of developing cancer in the United States is that approximately 11.2% of men will be diagnosed with prostate cancer at some point during their lifetime.

There is currently no registry for cases with prostate cancer in South Africa, other than a histology- based registry at the National Health Laboratory Service. “This registry only includes men who were biopsied for prostatic disease and the numbers are therefore an underestimate of the real numbers of prostate cancer. For this reason we also have no indication of the numbers of men in South Africa who died from prostate cancer.”

One of the possible reasons is that annual prostate cancer surveillance (PSA) is not routinely measured in men presenting at public hospitals. As a result, rural men especially may present late with advanced disease. Annual PSA testing is essential as it can help to detect prostate cancer early, through a simple blood test.

At the same time, Prof Bornman reiterates the recommendation of the South African Prostate Cancer Foundation, which emphasises the need for all men over 50 years to have both the digital rectal examination (DRE) and PSA screening. “The PSA blood test does not replace the DRE,” said Prof Bornman.

Black men older than 40 years with a family history of prostate cancer or breast cancer in a parent, sibling or cousin should go for regular testing, at least once a year, if there is no reason for concern. All men older than 45 years should know their PSA level. PSA testing should be available at public health care centres and coordinated efforts are crucial to create awareness in men and their partners of this disease.

Genomics will not provide the only answers to the development of prostate cancer. Other factors such as the burdens of environmental chemical pollution and infectious diseases have to be explored as possible contributing factors.

There is particular concern about high estrogenic exposures to hormone active substances also known as endocrine disrupter chemicals. These chemicals are found in clothing, furniture, electronics, many food and beverage containers, insecticides, detergents, plastic wraps, children’s toys etc. During pregnancy these chemicals are transferred to the developing foetus and may impact the developmental processes.

In rodent models, low-dose estradiol exposures (female hormone) during foetal development as well as exposures to environmentally relevant doses of the endocrine disruptor bisphenol A show increased incidence of prostatic lesions with aging. These lesions are believed to be the precursor lesions for prostatic adenocarcinoma and may provide a foetal origin of prostate cancer.

Professor Riana Bornman

August 16, 2018

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Researchers
  • Professor Riana Bornman
    Professor Riana Borman’s research seeks to understand the effects of endocrine-disrupting chemicals (EDCs) on human and environmental health, with a special focus on male reproduction. Most of her research is carried out in the rural areas of the Vhembe District in Limpopo, in communities where insecticide is sprayed to control malaria-carrying mosquitoes.
    She began her career in the Department of Urology at the University of Pretoria (UP) in 1980 and had a research topic to explore within the first week, which triggered a career-long curiosity. “I am still researching the role of EDCs on human health today,” she says.

    Prof Bornman, who obtained an MBChB at UP, says her research focus developed from her experiences in managing patients in clinical settings. “As a clinical physician, I realised that human and environmental health was intricately affected by environmental pollution, especially exposure to EDCs. Being a clinician at UP has created unique opportunities to conduct research in the Limpopo province.”

    Her field of research addresses the unintentional health consequences of annual indoor residual spraying of insecticides to control malaria-carrying mosquitoes. In the Vhembe District, dichlorodiphenyltrichloroethane (DDT) is sprayed to control these mosquitoes and reduce cases of malaria and death. While DDT is largely a banned chemical, according to the Stockholm Convention on Persistent Organic Pollutants, it is allowed in some countries, including South Africa, for malaria vector control.
    But there is growing concern around the adverse health effects associated with DDT. Scientific evidence from South Africa is crucial and contributes to the body of evidence that is calling for safer alternatives to DDT for malaria vector control.

    The chemical is effective for about six months and needs to be sprayed every year. Prof Bornman’s research shows that annual spraying has negative, long-term consequences for pregnant women and young children. “We are seeing these consequences in children, possibly persisting into future generations, suggesting long-term health effects. Our research collects important irrefutable scientific evidence of the health impacts of EDCs in communities exposed to insecticides.”

    Prof Bornman is the co-principal investigator for the Venda Health Examination of Mothers, Babies and the Environment (VHEMBE) study, which is being conducted in collaboration with Prof Brenda Eskenazi of the University of California, Berkeley in the US and Dr Jonathan Chevrier of McGill University, Canada. The VHEMBE study is the first birth cohort from a population that is currently exposed to DDT via annual spraying and is the biggest longitudinal birth cohort from Africa. The study group recruited and enrolled 752 mother-child pairs at Tshilidzini Hospital in Thohoyandou and have monitored the children up to eight and a half years of age for various possible health impacts.

    She hopes to continue doing research that contributes to improving the health of those whose voices are not often heard.

    She is also co-principal investigator and clinical leader of the South African Prostate Cancer Study, which is investigating the genomics of prostate cancer in African men; this is being done in partnership with Prof Vanessa Hayes, Scientific Director of the Garvan Institute of Medical Research in Sydney, Australia. A recent highlight in their research work has been funding awards from major international bodies to investigate the development of aggressive prostate cancer in black African men. “We are extremely motivated to continue with this research,” says Prof Bornman. “Successful awards reflect that the scientific leaders in our field support our approach.”

    Over the past 18 months, the prostrate cancer study group began a new project that focuses on the mutational signatures of DDT and the possible role of this EDC on prostate cancer aetiology. Prof Bornman is also the study leader for a new study on knowledge, attitudes and practices of traditional healers, primary healthcare service providers and men in the rural Vhembe District.

    She says in her research work she was inspired by Prof Dion du Plessis, former Head of Urology and Dean of the Faculty of Health Sciences at UP, who taught her to think beyond the obvious, to dream big and to just DO it!
    Her academic role model was Prof Carl Franz, former Head of Surgery at UP. He was a prime example of how to integrate laboratory and clinical medicine in an academic career, she says.

    Her message to school learners or undergraduates who are interested in her field is: “Every one of us, irrespective of our discipline, can make a difference in the lives of people. My research aims to improve the lives of people living with the constant threat of malaria under unforgiving environmental and socio-economic conditions. We can all do research that makes a difference. One just has to care enough about people.”

    Her hobbies are photography and travel.


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