The story of anal cancer and HPV – what is it?

Finding a potential supervisor for one’s independent academic research project is actually more about finding a project one can join. A good supervisor has a project that they take the lead on, hence they are called the principal investigator of scientific research group. The supervisor then introduces one to a half-baked idea that actually is part of their bigger project. Ideally the collaboration between student and supervisor leads to some wonderful results, where student takes the half baked idea and turns into something yummy for the consumption of academia and at best the general public.

Today I met with Kevin Rebe from the Health4Men project at the Ivan Toms Clinic in Woodstock, Cape Town. Let me start by saying I was so glad to meet him, as I went there in January, fresh off the bus from Namibia, to finally see the place where men who have sex with men go to find tolerant health professionals who will treat them right in a clinical setting.

Now Kevin is working on setting up a screening program for anal cancer. The goal of this, as any screening, is to detect individuals in whom the disease process has already begun, but the expression of disease – the clinical symptoms – are yet to appear. For this reason it is often though of finding individuals in the pre-clinical phase of a disease. AIDS is an easy example, the clinical phase is AIDS and the pre-clinical is when you are infected with HIV-1 but you have no signs and a strong immune system. The HIV-1 screening allows health providers to find out you carry this virus and they put you on treatment before your immune system suffers the consequences of uncontrolled HIV-1 entering, replicating in and decimating the white blood cells.

Now in terms of anal cancer the point is to find those individuals who are infected with etiological agent – one of the known Human Papiloma Viruses known to cause cancer (HPV 16,19) and those that probably do cause cancer (HPV 39). But it seems infection with these critters in the anus is not sufficient to cause cancer. Not everyone get’s cancer, as some people get rid of the virus, ‘ if you have a competent immune system, they resolve by themselves’ as Kevin explained. Once can imagine in which cases one would not have a competent immune system and thus be more at risk of getting anal cancer. If you have AIDS. Trouble is that if you have AIDS long enough, you probably will die of something else before cancer develops. Cancer is disease of the old in the developed world and it is not surprising because it takes time to develop. When someone has AIDS, they do not have much of that time, unless of course they develop one of those ‘AIDS characteristic cancers’ such as Kaposi Sarcoma – the skin cancer that the first known AIDS patients had. Now is anal cancer an AIDS characteristic cancer? I know that cervical cancer, which has a common cause with anal cancer, was initially not an ‘AIDS characteristic cancer’ among women in the US, but then the CDC classified it as such. I remember this from the documentary ‘End Game’ about AIDS in the US.

This brings me to an important point about screening programs. We learnt that good screening programs detect common diseases. These are not rare familial disease, but ones that are common enough among people that catching them early will allow one to prevent a great deal of death and suffering, which justifies the screening program. Indeed, with screening you basically evaluate patients en masse for disease markers or signs. This can be costly and must be justifiable.

I now need to understand what is the burden of disease of anal cancer. In the larger population, it is not that common, about 70 per 100 000 person years of follow up – if you took 100 000 random people an followed them for one year, you would get 70 cases of this cancer. However, in men who have sex with men, we expect this to be higher. In his blog ‘Warts and all! Bruce Little speaks about anal cancer risk being 17 times greater for men who bonk other men (or is it the other way round?) compared to straight men. Does the Health4Men project have a sense of the burden of disease among these men? (Notice I use the word ‘these’, not because I want to render men who have sex with men as ‘the other’, but to just maintain a distance between myself and my subject matter. Since I plan to do epidemiology, I cannot put myself in the mix.)

Then there is also understanding the story of anal cancer. How does it start? The infection with specific cancer causing HPV subtypes in the anus, which cause certain abnormalities in the anus itself. These abnormalities are then searched using techniques such as High Resolution Anoscopy and tissue sample or biopsy is needed to see if these are likely or unlikely to develop into cancer. Now where do anal warts fit into the picture? I assumed anal warts were indications of HPV infection, such as the cancer causing ones, but according to Bruce Little, ‘warts don’t turn into cancer?’. This has just left me very confused as to relevance of discussion anal warts in relation to anal cancer. Are they just used to indicate possible infection with cancer causing warts?

I think I really need to meet up with Kevin again and ask him one thing “if you had to write your NIH proposal for anal screening again, what information would like to include from the Health4men clinical records that I could weave together for you? What story do you think these records could tell?”


About writinghealth

Wannabe Epidemiologist? Wannabe med anthro person? I guess. Christian, scientist (not Christian scientist), i mean like I studied molecular biology and I part of the RC Church. I also completed a Masters of Public Health, at the University of Cape Town, in Epidemiology and Biostatistics.
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