When I first started my research into Anal SCC, I was told by multiple clinicians that the rise in incidence of ASCC in England is due to the relaxation of social stereotypes and the rise of sexual freedom. In particular in women, who were within the first generation to benefit from oral contraceptives and the rise of feminism.
To put bluntly; women were more able to have sexual relationships and therefore were more likely to be exposed to different strains of HPV from different partners.
Their evidence for this was that this patient subgroup are associated with the highest incidence increase worldwide and that patients in England are more likely to be female Caucasians in their 60’s and 70’s.
However the more I read about Anal SCC the more I think that it cannot be so simple.
Firstly, this generation would have been within the first cohorts of cervical screening, although the risk of cervical cancer is increasing over the last few years (in particular in younger women who did not participate in screening) there is a net reduction in cervical cancer incidence by 24% in the UK since the 1990’s. However, geographical areas with high incidence rates of cervical cancer are not necessarily associated with high incidence rates of Anal SCC.
Secondly, as the highest risk of ASCC is actually associated with being an HIV positive MSM, is the risk actually associated with receptive anal intercourse?
In demographic areas where HIV prevalence is high, the majority of patients seen with Anal SCC and AIN are HIV positive MSM. There is less of an association with HIV negative MSM.
There are some papers in the literature that demonstrate a higher risk of AIN in women and men who practice receptive anal intercourse, however there are also papers that also show that there is no difference identified between sexual practices and risk.
I think this theory is difficult to prove, firstly due to recall bias, sexual practices change over time, just because you practiced receptive anal intercourse with one partner does not mean that you regularly do so. Nor does it mean that interaction was the time you were exposed to an oncogenic HPV. Patients can also be, understandably sensitive about their sexual practices and not wish to disclose them. In particular the paper I refer to above which did not show a different with sexual practices and risk, the group denying receptive anal intercourse were statistically older. It’s possible that this group were less likely to disclose due to social stigma.
Like cervical cancer, Anal SCC has been associated with promiscuity and a higher number of sexual partners. There are some interesting papers that suggest patients with sexually transmitted infections are more likely to have High Grade AIN. I also think that this is not the most simple answer as being exposed to sexually transmitted infections also increases your risk of HIV which is known to be a much greater risk factor in AIN and Anal SCC.
Unfortunately, at the moment the data we have is limited by the clinical data we have access to. From talking to female patients, in particular, after a diagnosis with Anal SCC, they do report concerns about social stigma that Anal SCC is a cancer associated with promiscuity and sexual practices.
I think that this is unfair as although, in theory, promiscuity increases your likelihood of eventually becoming infected with an oncogenic HPV, you do not need to have multiple HPV exposures before unfortunately becoming infected with a high risk one.