Anal canal cancer

Four-fifths of all anal cancers arise from the anal canal.

5280 cases in the US in 2011 with approximately 770 deaths (Jemal A et al).

Account for approximately 2% of gastrointestinal cancer in the U.S. and the incidence has double over the past three decades.

Extends from the opening of the anus to the internal anal sphincter about 4 cm in length: the lowest 2 cm is cutaneous tissue and the upper 2 cm is covered by mucosa.

A rare disease that accounts for less than 1% and 3% of all new cancer diagnoses and gastrointestinal tumors, respectively.

Extends from the perianal skin (the anal verge) to the rectal mucosa.

Incidence continues to climb.

90% of cases are squamous cell in origin.

The dentate line represents the end of the squamous mucosa and the beginning of the zone of transition from squamous to nonsquamous mucosa.

Tumors can be keratinizing or nonkeratizing depending on the location in relation to the dentate line.

The most common histological subtype squamous cell carcinoma with an annual incidence of 0.5 to 2.0 in 100,000.

The incidence is increasing.

The five year overall survival has increased.

Keratinizing and nonkeratizing cancers have similar biology and prognosis.

Consists of a sphincter muscle complex at the level of the puborectalis muscle, multiple types of mucosa with sensory nerves, anal glands and vascular hemorrhoidal channels.

squamous cell carcinoma of the anus and its precursor lesion, anal intraepithelial neoplasia are mostly attributable to human papillomavirus infection, which represents the causative agent in 80-85% of patients.

HPV 16 and HPV 18 are the major subtypes.

Anal intercourse in a high lifetime number of sexual partners increases the risk of persistent HPV infection leading to malignancy.

Additional important risk factors include HIV infection, prior history of anogenital warts, lower genital tract malignancies, immuno suppression in transplant recipients, history of HPV related other cancers, autoimmune disorders and cigarette smoking.

Patients may present with bleeding and diagnosis may be delayed because bleeding is attributed to hemorrhoids.

Clinically anal cancer may present with a mass, a nonhealing ulcer, pain, bleeding, itching, discharge, fecal incontinence and fistula.

Digital anal rectal examination is essential for clinical diagnosis.

The diagnosis is made by biopsy proven histology.

HPV vaccination is expected to result in lower incidence of anal carcinoma.

Primary tumor assessment is done by MRI exam, however CT scan seven thorax abdomen and pelvis may be required to assess potential metastatic disease sites.

Patients with HPV positive tumors have improved disease free survival as compared with patients with HPV negative disease.

Patients with skin ulceration, nodal involvement and male sex have increased risk for a local regional failure.

Patients must be evaluated for the HIV status.

Primarily associated with men having sex with men, however 60% of patients are women.

Risk factors, men having sex with men, multiple sexual partners, history of sexually transmitted disease, receptive anal intercourse, previus human papilloma virus infection, chronically immune suppression, organ transplantation, chroninc steroid use, tobacco use and a history of HIV,

Average age of a paitent is 60 years.

Average age of non-HIV positive patient with anal canal cancer is 60 years.

Average age of HIV positive disease patient with anal canal cancer is in the 40s.

Low tendency to disseminate locoregional is of major importance to the outcome of patients.

80% of patients present with locally advanced disease.

Metastatic disease develops in 15-20% of patients.

Squamous cell cancer of the anus is usually preceded by intraepithelial dysplasia or neoplasia that progresses to invasive cancer.

Clinical exam includes digital examination of the rectum, nodal exam, particularly of the inguinal region, proctoscopy for T staging, CT, MRI or PET scan of chest abdomen and pelvis.

Surgery is curative for locally advanced squamous cell carcinoma of the anal canal, but it requires an abdominal perineal resection, therefore chemoradiation is pref2242ed.

Radiation therapy as a single modality is not effective as combining it with chemotherapy.

Radiation as a single modality results in local control in only 68% of all patients with anal canal cancer T1-T2: 78-81%, T3 63%, And T4 33%.

Preoperative chemotherapy and radiation results in high pathological complete remission rates of 80%.

Optimal treatment of regimen of 5 FU, mitomycin and concurrent radiation therapy.

Surgery is now reserved for residual or recurrent disease.

The most proximal portion of the anal canal drains into the lymph nodes of the inferior mesenteric system.

Inguinal metastases in 10-25% of patients.

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