Less than one in twenty people with HIV at highest risk of anal cancer received screening for the condition in 2019 in the United States and around one-third had no access to screening through their care facility, a Centers for Disease Control and Prevention (CDC) study has found.
However, another recent study has found that anal self-examination or examination by a partner enabled detection of early-stage anal cancer lesions with a high degree of agreement with clinician exams, allowing earlier treatment. Self-examination may serve as a useful community-led tool for raising awareness of the need for anal cancer screening.
People with HIV are between 19 and 28 times more likely to be diagnosed with anal cancer than the general population in the United States. Incidence is highest among gay and bisexual men (about 89 cases per 100,000 per year).
The first line of anal cancer screening is the anal cytology test, or Pap smear. This test is used to collect cells from the anal area that can be viewed under a microscope to look for changes suggestive of cancer. Changes in anal cells are graded, from low-grade lesions that need to be reviewed again in the future, to high-grade lesions that need immediate examination using high-resolution anoscopy (HRA). A tissue sample from the lesion is taken under anaesthetic and examined under a high-resolution microscope to detect cancerous changes in cells.
Cancer specialists have been slow to develop guidelines on how often people at higher risk of anal cancer should undergo screening, due to a lack of evidence from randomised studies until recently. In 2022 a major study showed that treating precancerous lesions reduced the risk of anal cancer in people with HIV. Guidelines issued by anal cancer specialists in 2024 recommended annual screening but there is no US national recommendation. There is also a shortage of doctors trained to carry out high-resolution anoscopy, so access is uneven.
The CDC collected data in 2019 from people with HIV receiving care in 16 US states and Puerto Rico, and from the health facilities providing their care in 2021. They looked at the characteristics of people in care, the proportion who underwent anal cancer screening and how screening was accessed, whether onsite or by referral to another provider.
The survey identified 3136 people with HIV at highest risk for anal cancer, including 1656 gay and bisexual men and transgender women aged 35 or over, and 1480 other people with HIV aged 45 or over. The survey sample also included people 964 people with HIV not considered at higher risk.
The study population was 41% Black or African-American, 29% White and 22% Hispanic, 74% male and 2% transgender female. Almost two-thirds (63%) were aged 45 or over.
A high proportion of the sample were unemployed or unable to work (41%) and living at or below the federal poverty level (41%), 54% were reliant on public health insurance and 11% either relied on Ryan White funding to cover the cost of care or had no health insurance coverage at all.
One-third of the sample had had detectable viral load measurements in the previous year, 14% had advanced HIV-related symptoms in the previous year and 57% had had symptoms related to HIV in the past.
"Providers are reluctant to offer smear testing if they cannot carry out follow-up HRA testing if abnormalities are detected."
Just under 5% of people with HIV at highest risk of anal cancer (4.8%) had received screening in the form of a smear test in the previous year. A higher proportion of gay and bisexual men and transgender women over 35 had received screening (a prevalence difference of 3.8%, p=0.006)). But compared to Non-Hispanic Whites in the sample, Black/African-Americans were significantly less likely to have undergone screening (prevalence difference -2.8%, p=0.027). Screening prevalence was significantly lower in people with high school education or less compared to those with post-high school education, and in the unemployed or those unable to work compared to those in employment. Screening prevalence was also significantly lower in people with detectable viral load, in heterosexual people and in people in Southern states.
The study found that 22% of the sample who had abnormal smear test results received care at sites which provided high-resolution anoscopy (HRA) screening, while 45% received care at sites which referred patients to another provider for HRA. Thirty-two percent received care at sites which provided no on-site screening or established referral pathway. There were no significant differences in access to HRA by race or ethnicity, by gender, age or education among people with HIV. People with HIV were more likely to be receiving care at facilities with onsite access to HRA if they had advanced HIV or a CD4 count below 200 in the past year.
The study investigators say that the lack of capacity to provide HRA screening is a major constraint on screening, because providers are reluctant to offer smear testing if they cannot carry out follow-up HRA testing in cases where abnormalities are detected. High resolution anoscopy is technically challenging and clinicians need training in how to carry it out to a high standard.
“There is a critical need for greater patient and provider education and awareness about risk factors for anal cancer and about prevention,” they conclude.
Rim SH et al. Prevalence of anal cytology screening among persons with HIV and lack of access to high-resolution anoscopy at HIV care facilities. Journal of the National Cancer Institute djae094, 2024.