Impact of screening and antiretroviral therapy on anal cancer incidence in HIV-positive MSM. AIDS
Blaser et al. aimed to model the impact of screening strategies and combination antiretroviral therapy (cART) coverage on anal cancer incidence in Switzerland. The authors developed an individual-based mathematical simulation model to predict anal cancer incidence in HIV-positive men-who-have-sex-with-men (MSM) in Switzerland, 1980-2030. In the CD4 count dependent strategy, only those MSM were screened who had had a CD4 nadir below 200 cells/μl.
Modeled anal cancer incidence peaked at 81.7/100,000 in 2009, plateaued 2010-2015 and decreased to 58.7 by 2030 with stable cART coverage, and to 52.0 with 100% cART coverage. With yearly cytology, incidence declined to 38.2/100,000 by 2030, with yearly anoscopy to 32.8 and with CD4 count guided anoscopy to 51.3. The numbers needed to screen over 15 years to prevent one anal cancer case were 384 for yearly cytology, 313 for yearly anoscopy and 242 for CD4 count dependent screening.
In conclusion, the modelling study predicts substantial reductions in anal cancer incidence in MSM in the next 15 years, even in the absence of screening and without further increases in cART coverage. The introduction of yearly anal Pap screening or anoscopy screening, or CD4 cell count guided anoscopy screening would reduce anal cancer incidence further. Notably, the numbers needed to screen to prevent one invasive anal cancer in MSM appear to be lower than the numbers needed to screen to prevent one invasive cervical cancer in HIV-negative women.