Screening for anal cancer in men who have sex with men (MSM) — with pap smears, high resolution anoscopy, with whatever test — is quite the quagmire.
As I’ve mentioned before, the proponents of screening cite the success of cervical cancer screening and the startling high rates of anal cancer among HIV+ MSM as reason enough for doing something.
(Exactly what we should be doing is far from clear.)
The naysayers, who are much less vocal, say there is no evidence that this screening actually reduces the rate of anal cancer, which is of course the endpoint of interest.
Now, over in Lancet Oncology, comes this paper entitled, “Anal human papillomavirus infection and associated neoplastic lesions in men who have sex with men: a systematic review and meta-analysis.”
After reviewing a dizzying amount of data, the authors conclude:
Anal HPV and anal cancer precursors were very common in MSM. However, on the basis of restricted data, rates of progression to cancer seem to be substantially lower than they are for cervical pre-cancerous lesions. Large, good-quality prospective studies are needed to inform the development of anal cancer screening guidelines for MSM.
Not to beat a dead horse here, but the fact remains that just because we can screen for pre-cancerous lesions, doesn’t mean we should.
(For more on this fascinating dilemma, read this op-ed piece. Or this recent survey.)
And it is notable that two established HIV guidelines — those for prevention of opportunistic infections and for HIV primary care — do not endorse anal pap smear screening, awaiting just the sort of prospective studies called for in this paper.