Anal cancer
Anal cancer refers to malignancies affecting the anal canal and surrounding regions, including the perianal skin. It is a relatively rare form of cancer, accounting for about 4% of alimentary tract cancers, but its incidence is rising, particularly among men, including those who are HIV-positive. The primary risk factors associated with anal cancer include infection with high-risk strains of the human papillomavirus (HPV), particularly serotypes 16 and 18, along with high-risk sexual behaviors and immunosuppression. Symptoms may vary, with common signs including bleeding, itching, and pain, although some individuals may be asymptomatic.
Diagnosis typically involves a combination of physical examinations, imaging studies, and biopsies to confirm the presence of cancerous cells. Treatment options can include surgery, radiation therapy, and chemotherapy, with the specific approach depending on factors such as tumor size, location, and type. Prognosis is generally better for smaller, well-differentiated tumors, and those not involving lymph nodes. Preventative measures may involve HPV vaccination and lifestyle changes to reduce risk factors. Current discussions around screening, particularly anal Pap tests for high-risk populations, are ongoing, as early detection can lead to more effective treatment outcomes.
Anal cancer
ALSO KNOWN AS: Cancer of the anal canal, anorectal cancer, rectal cancer, anal neoplasia, Bowen disease, Paget disease, HPV-related anal dysplasia, anal intraepithelial neoplasm
ANATOMY OR SYSTEM AFFECTED: Anus, gastrointestinal system
DEFINITION: Cancer affecting the lower alimentary tract, including the interior anal canal from the anorectal ring to the anal verge with 5 centimeters of skin extending beyond, including the perianal skin.
CAUSES: Human papillomavirus (HPV) serotypes 16 and 18, high-risk sexual activity, immunosuppression
SYMPTOMS: Bleeding, itching, pain; may be asymptomatic
DURATION: Chronic
TREATMENTS: Surgery, radiation, chemotherapy
Causes and Symptoms
The Human papillomavirus (HPV) , especially serotypes 16 and 18, is believed to be a major risk factor for anal cancer. Receptive anal intercourse is a risk (but not a necessary factor) in acquisition of the virus. A history of sexually transmitted infection and/or multiple sexual partners and immunosuppression, including from HIV-AIDS, are also associated with an increased risk. Women with cervical or vulvar cancer are at an increased risk for developing anal cancer.
The symptoms depend on the area affected and the cell types. Some cell types, such as squamous cell and basaloid squamous carcinoma, are most likely to cause bleeding. A mass may be present upon examination, but it will not be noticed by most patients, and or is not a significant symptom in most cases. Perianal carcinoma is more likely to cause itching.
Treatment and Therapy
Physical examination may include any of the following: a digital rectal exam, cytology (anal Pap), high-resolution with 3 percent acetic acid, proctoscopy, and of the inguinal lymph nodes. Biopsy must be done to confirm the diagnosis of abnormalities, with examination of the inguinal lymph nodes for metastatic disease. Additional studies for include lung films, liver enzyme studies, computed tomography (CT) scans, endoscopic ultrasound, and examination of any additional presenting symptoms related to other body systems.
Anal cancer is staged from 0 to IV, with stage 0 having the best prognosis. Outcomes for anal cancer depend on the following: the size of the lesions (smaller lesions correlate with improved over larger lesions); the location of the lesions (those in the perianal skin have a better prognosis than those deeper in the anal canal); of the tumors (well-differentiated tumors correlate with a better prognosis than tumors that are poorly differentiated); and involvement or other of the (lack of nodal involvement or other tumor extension improves prognosis). About 50 percent of anal cancer is diagnosed through localized lesions. General rates are estimated at 14 percent, meaning that most patients have a good prognosis.
Because of the rare nature of this cancer, studies on preferred treatments have been limited, and treatment is guided by individual factors such as site of involvement, size of lesion, cell type and differentiation, and extension beyond the primary lesion. Treatment may involve surgical removal of the lesion, chemotherapy, and radiation. Most management is now done with and with 5-fluorouracil (5-FU) and mitomycin. Radiation accounts for most of the treatment-related toxicities; however, new developments such as intensity-modulated radiation therapy (IMRT) may decrease adverse effects, and there are ongoing investigations into less toxic and more efficacious chemotherapeutic regimens, especially the substitution of cisplatin for mitomycin or combination of the two agents. Recommendations call for close medical follow-up after treatment.
Perspective and Prospects
Anal cancer is relatively uncommon, making up only about 4 percent of cancers of the alimentary tract. However, rates are increasing, especially among men and, in particular, HIV-positive men. Approximately 10,540 cases (3,360 in men and 7,180 in women) are diagnosed yearly in the United States. The American Cancer Society estimated that 2.190 people will die of the disease in 2024.
Prevention may be conferred by the expanded availability of vaccines against HPV and by lifestyle modifications to reduce sexual risk. Screening guidelines for the performance of anal Paps are in flux, but these tests have become more widely available with liquid-based cytology. Discussion of the use of anal Pap tests is ongoing, particularly for HIV-positive individuals at an increased risk for anal cancer. Anal Pap may diagnose anal intraepithelial neoplasia (AIN), the development of precursor lesions similar to cervical intraepithelial neoplasia (CIN), the development of precursor lesions to cervical cancer. Detection of precursor lesions by Pap testing can then be followed by high-resolution anoscopy, similar to cervical colposcopy. Early diagnosis of AIN may lead to effective treatment, similar to diagnosis of CIN; however, the lack of standard screening recommendations and limited resources for the referral of patients with positive anal Pap findings limit many clinicians from screening.
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