Anal Cancer Detection (Mejia Powell, 9/17/25)

 A recording of this presentation is available HERE.

Dr. Rob Mejia Powell gave a really awesome talk this week about Anal Cancer Screening. He reminded us that, while anal squamous cell carcinoma-- almost entirely HPV-related -- is rare in the overall population (1-2 cases/100K person years). While most people are not high risk and should NOT be screened, there are higher risk populations who should definitely be screened with anal pap smears and referred to high resolution anoscopy (HRA), which is available through SRCH for internal and external referrals. Take a look at his presentation for some really great info. If you just want the brief notes, you'll miss out on the butt jokes. 

Here's a reminder of what patients with anal cancer "look like", survivors of anal cancer:   https://youtu.be/QYR3GWWAmjE?si=kolJuD1TrdgWXMBU

"Say the word 'anal anal anal' a million times until your friends get used to it."

Take a look at this table to see the relative incidence in certain risk categories:

Known risk factors include age, HPV infection (especially vulvar neoplasia in women), receptive anal intercourse, and immunosuppression (e.g. HIV, chronic steroid/immunosuppressants). Also note that the highest growing group in women.

Pathogenesis of anal cancer is similar to cervical cancer:  Exposure to HPV > persistent infection > precancerous high-grade squamous intraepithelial lesions (HSIL, anal intraepithelial neoplasia (AIN grades 2 or 3)) > invasion to ASCC

Who should be screened?

• People with HIV
• MSM (especially with HIV)
• Women with history of cervical/vulvar/vaginal neoplasia
• Transgender women
• Solid organ transplant recipients, IBD (esp perianal Crohn's) and those on chronic immunosuppressants

Does screening work?

The ANCHOR Trial, published in NEJM 2022 was a multi-site RCT that showed that, YES, screening at risk populations does work to prevent anal cancer. Primary outcome: anal cancer. Test subjects: Men with HIV age >35. Study found 9 anal cancers in the treatment group (those screened>> HRA>> treatment) vs. 21 cancers in the observation group. This equates to a 60% decrease in anal cancer.

How to approach the topic of anal cancer screening with patients:

1) Explain what an anal pap smear is: what are we looking for? what are we trying to prevent? 

2) Get an HPI: anal itching? bleeding? pain? difficulty stooling? presence of anal lesions?

3) Anal Pap: get cytology and HPV prior to digital exam>> use Dacron swab (wet with water, place 2-3 inches across anal verge, aggressive angling)

4) Digital anal rectal exam (DARE)

5) Refer abnormal anal paps to high res anoscopy (HRA) (see chart)

Summary chart: