Anal cancer is rare–much less common than cancer of the colon or rectum. The American Cancer Society estimates for anal cancer in the United States for 2024 are:

• About 10,540 new cases (3,360 in men and 7,180 in women)
• About 2,190 deaths (1,000 in menand 1,190 in women)
• The risk of anal cancer in the general population is about 1.7 cases per 100,000 people.

Fig 20.3 ASCRS Textbook of Colon and Rectal Surgery - Squamous cell cancer of anus

POPULATIONS AT ELEVATED RISK

The risk of anal cancer is much higher in several populations, including people with HIV, men whohave sex with men (MSM), solid organ transplant recipients and women with a history of vulvarcancer or precancer. These groups all have at least atentimes increased rate of anal cancer, withsome groups being even higher, such as MSM with HIV.Other elevated risk groups include people with a history of vaginal or cervical pre-cancer or cancer,people with a history of anal warts, persistent (>1 year) high risk subtype HPV infection andpatientswith autoimmune conditions or requiring immunosuppressive medications.The number of new anal cancer cases has been rising for many years. Anal cancer is rare in people younger than 35 and is found mainly in older adults, with an average age being in the early 60s. It isalso more common in White women and Black men. Prevention and screening of high-risk populations are key parts in decreasing the rates of analcancer and effectively treating the disease when it occurs.A recent study (ANCHOR) shows that treatment of precancerous lesions in high-risk populations will decrease the risk of anal cancer in the future.

SCREENING

There are several screening methods used, especially in high-risk patient populations (see above). Screening methods will be limited to availability of certain procedures in any given region, but youshould ask your provider for a referral to the screening and treatment options that best fit your needs.

• Regular examination–Any patient with a history of anal and genital warts should have a regular examination for recurrence. The timing of examination will be based on each individualcase, but any warts or dysplasia that recur should be closely watched and treated. An examinationshould include visual inspection, digitalrectal examination (feeling inside the anus with a finger for any abnormality) and anoscopy (looking into the anus with a lighted scope) for patients with ahistory of anal disease.It is important for patients with genital HPV infection to also have an analexamination sincethe virus spreads through direct contact and is aided by bodily fluids.
• Anal cytology–This is the same testing as a Pap smear in a gynecology exam. A moist swabis inserted into the anus (or isself-insertedin some clinics) andrandom cells are captured andexamined under a microscope. If there are abnormal cells present, more testing may be recommended. The swab can also be tested for the presence of the HPV virus. They are not aperfect test and can have falseresults buthavea role in the screening ofhigh-riskpatients.
• High resolution anoscopy (HRA)–This is a procedure like colposcopy in a gynecology exam. This examination is usually done in the office and is tolerated well by most patients.The anal canalis stained with swabs using a small plasticanoscope andthe anal canal and surrounding skin isexamined with a special microscope. Biopsies of abnormal areas can be doneto determine if thereare precancerous changes. A recent study (ANCHOR) showed that examination with HRA inhigh-riskpatients, and treatment ofhigh-gradedysplasia (HSIL) led to decreased rates of anal cancer

PREVENTION

Although few cancers are totally preventable, avoiding risk factors and getting regular checkups are important. Using condoms may reduce, but not get rid of the risk of HPV infection. HPV vaccines (for those ages 9 to 26) have been shown to not only lower the risk of HPV infection, but also reduce the risk of anal cancer in men and women. People at increased risk should talk to their physicians about getting an anal cancer screening. During this test, your physician swabs the anal lining, looking at the cells under a microscope for anything unusual. Other forms of screening include looking closely at the area during a surgery, or in the office with a special scope to look in the anal canal. Early identification and treatment of precancerous areas may help prevent anal cancer. 

IANS (International Anal Neoplasia Society) CONSENSUS GUIDELINES FOR ANAL CANCER SCREENING

These guidelines are based on an increased risk by a factor of ten (10 times more likely to develop anal cancer over the general populations at the listed ages)

• 35 years of age - men who have sex with men (MSM) and transgender women (TW) with HIV infection
• 45 years of age–HIV + patients (non-MSM/TW) and MSM and TW without HIV infection
• Solid organ transplant recipients–screening should begin 10 years post transplantation
• History of vulvar pre-cancer or cancer–screening starts within one year of diagnosis

TREATMENT of ANAL WARTS

External warts can be treated by applying medications or by surgical removal. Topical medicinesarenotrecommended for use inside of the anus, so surgery for internal anal warts is required.

Medications for treatment of internal warts can either be chemicals that:

• Destroy the wart tissue (trichloracetic acid or podophyllin)
• Freeze the warts (liquid nitrogen)
• Help the immune system attack the warts (veregen, imiquimod)

• Destruction with electrical energy
• Surgical excision with scissors or a scalpel
• Laser destruction

TREATMENT OF ANAL DYSPLASIA

TREATMENT OF ANAL CANCER

• Local excision by surgery (for smaller tumors that do not involve the sphincter muscle or that can be removed with clear margins)
• Chemotherapy and radiation (Nigro protocol)
• Surgical removal of the rectum and anus with colostomy (for recurrent cancer or for acancer that does not respond to chemotherapy and radiation)

POST-TREATMENT

WHAT IS A COLON AND RECTAL SURGEON?

Colon and rectal surgeons are experts in the surgical and non-surgical treatment of diseases of the colon, rectum and anus. They have completed advanced surgical training in the treatment of these diseases as well as full general surgical training. Board-certified colon and rectal surgeons complete residencies in general surgery and colon and rectal surgery, and pass intensive examinations conducted by the American Board of Surgery and the American Board of Colon and Rectal Surgery. They are well-versed in the treatment of both benign and malignant diseases of the colon, rectum and anus and are able to perform routine screening examinations and surgically treat conditions if indicated to do so.

DISCLAIMER

The American Society of Colon and Rectal Surgeons is dedicated to ensuring high-quality patient care by advancing the science, prevention and management of disorders and diseases of the colon, rectum and anus. These brochures are inclusive but not prescriptive. 
Their purpose is to provide information on diseases and processes, rather than dictate a specific form of treatment. They are intended for the use of all practitioners, health care workers and patients who desire information about the management of the conditions addressed. It should be recognized that these brochures should not be deemed inclusive of all proper methods of care or exclusive of methods of care reasonably directed to obtain the same results. The ultimate judgment regarding the propriety of any specific procedure must be made by the physician in light of all the circumstances presented by the individual patient.