Early treatment prevents anal cancer in people living with HIV: ANCHOR study stops early

Simon Collins, HIV i-Base

For many years, the lack of randomised data has limited screening programmes for anal cancer, even though rates are significantly higher in people living with HIV than in the general population.

A large phase 3 US study has now reported significant benefits from active treatment. Although detailed results have not been published, based on a report from the Data and Safety Monitoring Board (DSMB) all participants will now be offered treatment. [1]

This is years earlier than expected, so although the actual results are not reported, the difference between arms must be significant for the primary endpoint.

The Anal Cancer/HSIL Outcomes Research (ANCHOR) study has so far enrolled almost 4500 HIV positive adults (out of a target of more than 5000). Participants need to have precursor lesions for anal cancer and randomisation is to either removal (usually with electrocautery) or to monitoring. [2, 3]

Similar to studies in cervical cancer, the results show that screening and removing high-grade squamous intraepithelial lesions (HSIL), significantly reduce the risk of progression to anal cancer.


The ANCHOR study is an amazing achievement – not least for the participants who volunteered and were in the control arm. It took many years to plan and enrol and results will change guidelines.

However, the press release should include top-line results for such an important study, and these will hopefully be released shortly.


  1. University of California at San Francisco (UCSF) press release. Treating anal cancer precursor lesions reduces cancer risk for people with HIV. (7 October 2021).
  2. Topical or ablative treatment in preventing anal cancer in patients with HIV and anal high-grade squamous intraepithelial lesions (ANCHOR).
  3. ANCHOR Study website.

This report was first published on 7 October 2021.

Links to other websites are current at date of posting but not maintained.