Treatment of Anal High-Grade Squamous Intraepithelial Lesions to Prevent Anal Cancer in Persons With HIV

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In the phase III ANCHOR study reported in The New England Journal of Medicine, Palefsky et al found that treatment of high-grade squamous intraepithelial lesions was successful in preventing anal cancer vs active monitoring in persons infected with HIV.

Study Details

In the multicenter trial, 4,446 patients aged ≥ 35 years were randomly assigned between September 2014 and August 2021 to receive treatment (n = 2,227) or active monitoring (n = 2,219). Treatment included office-based ablative procedures, ablation or excision under anesthesia, or the administration of topical fluorouracil or imiquimod, with treatment continuing until high-grade squamous intraepithelial lesions were completely resolved.

The primary endpoint was progression to anal cancer.

Key Findings

In the treatment group, initial treatment included office-based electrocautery ablation in 83.6% of patients, infrared coagulation in 4.8%, ablation or excision under anesthesia in 2.3%, topical fluorouracil in 4.5%, and topical imiquimod in 0.5%.

During a median follow-up of 25.8 months, there were 9 cases of anal cancer in the treatment group (173 per 100,000 person-years, 95% confidence interval [CI] = 90–332) vs 21 cases in the active monitoring group (402 per 100,000 person-years, 95% CI = 262–616). This represented a 57% (95% CI = 6%–80%) reduction in risk in the treatment group (P = .03). The cumulative incidence of progression to anal cancer at 48 months was 0.9% vs 1.8%.

Among the nine patients in the treatment group who developed cancer, eight were initially treated with electrocautery and one with infrared coagulation.

On multivariate analysis among all patients, lesion size of > 50% vs ≤ 50% of the anal canal or perianal region was associated with increased risk of progression to cancer (hazard ratio = 5.26, 95% CI = 2.54–10.87). Nadir CD4 count was not significantly associated with risk.

Serious adverse events occurred in seven patients (most commonly, infection/abscess due to anal biopsy) in the treatment group and one in the active monitoring group.

The investigators concluded, “Among participants with biopsy-proven anal high-grade squamous intraepithelial lesions, the risk of anal cancer was significantly lower with treatment… than with active monitoring.”

Joel M. Palefsky, MD, CM, of the University of California, San Francisco, is the corresponding author for The New England Journal of Medicine article.

Disclosure: The study was funded by the National Cancer Institute. For full disclosures of the study authors, visit

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