Anal Cancer

Carcinoma of the anus is relatively rare: only 1–2% of all cancers of the large intestine and anus

Squamous cancers (keratinizing, transitional cell, and cloacogenic), 80%; adenocarcinomas, 20%

Increased incidence among

• People practicing receptive anal intercourse

• Those with a history of anorectal warts

• Those with HIV infection

Human papillomavirus (HPV) infection in > 80%

Increased risk in combined HIV and HPV infection

Anal bleeding

Pain

Local tumor

The lesion is often confused with hemorrhoids or other common anal disorders

Tumors tend to become annular, invade the sphincter, and spread upward via the lymphatics into the perirectal mesenteric lymphatic nodes

CT or MRI scans of the abdomen and pelvis are required to identify regional lymphadenopathy or metastatic disease at diagnosis

PET imaging may be used in conjunction

Wide local excision for small (< 3 cm) superficial lesions of the perianal skin

Combined-modality therapy for tumors invading the sphincter or rectum: external radiation with simultaneous chemotherapy (fluorouracil plus mitomycin)

Local control achieved in approximately 80% of patients

Radical surgery (abdominoperineal resection) for patients in whom chemotherapy and radiation therapy fail

Metastatic disease is generally treated with either carboplatin and paclitaxel or 5-fluorouracil in combination with cisplatin

Checkpoint inhibitor therapy with either nivolumab or pembrolizumab

• Has been shown in small studies to result in disease control in up to 46% of patients with chemotherapy-refractory, metastatic or unresectable disease

• Should be strongly considered in the second-line setting in patients with good performance status

5-year survival rate

• 81% for localized (stages I–III) disease

• ~30% for metastatic (stage IV) disease

In a large controlled trial, HPV vaccination of healthy men (16–26 years old) who have sex with men decreased the incidence of anal intraepithelial neoplasia by 50%