Anal Carcinoma | Anal Cancer: Information on Symptoms, Treatment Options, and Prognosis

Anal cancer is a form of colorectal cancer. However, anal cancer accounts for only two percent of all colorectal cancer cases. This type of cancer is therefore one of the rarer malignant tumors of the colon and rectum. 

Anal canal carcinoma primarily affects women, while men are more likely to develop anal margin carcinomas. Most anal carcinomas occur after the age of 60.

The malignant tumor forms either in the anal canal, at the anal margin, or in the surrounding skin and mucous membrane area. Most cases are squamous cell carcinomas that occur above or below the linea dentata. 

The classification is as follows:

• Anal canal carcinoma: a tumor that originates in the anal canal
• Anal margin carcinoma: a tumor that originates in the skin of the anus

Both forms are collectively referred to as “anal cancer,” but they differ in extent, growth patterns, and treatment strategies. Only a few people are diagnosed each year (approximately 1 in 500,000), but the disease is among the cancers that can cause functional limitations due to its location near the rectum. 

The development of anal cancer is multifactorial, involving several known risk factors.

HPV as the Main Factor

Infection with human papillomaviruses (HPV), particularly the high-risk types HPV 16, 31, and 33, plays a central role. Up to 85% of patients test positive for HPV. The viruses are sexually transmitted, primarily during sexual intercourse. There is an increased risk for individuals with multiple sexual partners or those with sexually transmitted infections. 

Chronic Mucosal Damage

Long-standing inflammation, chronic infections, or injuries in the anal region can contribute to the development of anal cancer. Conditions such as Crohn’s disease or ulcerative colitis lead to long-term changes in the tissue, which can promote the development of cancer cells.

Immune deficiency

A generally weakened immune system or an immune system weakened by HIV increases the risk of developing anal cancer. The body is then less effective at fighting off abnormal cells. 

Smoking and Other Risk Factors

Nicotine is also considered a significant risk factor. Furthermore, mistaking the condition for hemorrhoids can lead to the initial signs being overlooked. If symptoms resembling hemorrhoids occur, a medical evaluation should be conducted if the course of the condition is atypical. 

The symptoms of anal cancer are often nonspecific and are initially not associated with cancer.

Typical symptoms include:

• Traces of blood on the stool or clearly visible blood in the stool
• Pain during bowel movements
• Itching or a sensation of itching in the anal area
• A sensation of a foreign body, especially if the tumor narrows the anal canal
• Changes in stool consistency 
• Irregular bowel movements, diarrhea, or constipation
• Fecal incontinence if the sphincter muscle is affected

Sometimes anal cancer has already spread to the vagina or surrounding structures. Swollen lymph nodes in the groin may indicate metastasis.

If anal cancer is suspected, a standardized diagnostic workup is performed according to guidelines. 

First, a physical examination is performed, including a visual inspection of the anus and anal region. A digital rectal examination is also essential to palpate for hardening or lumps in the anal canal.

This is followed by a rectoscopy, which allows for direct assessment and the collection of a tissue sample. This sample is analyzed histologically to provide a definitive diagnosis.

Additional imaging tests, such as CT, MRI, or ultrasound, are also performed to check whether lymph nodes are affected or whether metastases are present. 

For classification purposes, anal cancer is divided into different stages, which significantly influences treatment. 

Treatment depends on the extent of the disease, the tumor size, and the type of carcinoma (anal canal carcinoma or anal margin carcinoma).

The following treatment options are currently available:

Surgical

Smaller tumors on the anal margin are often removed surgically. During this procedure, the surrounding tissue is also resected to a safe margin.

For larger anal carcinomas, or if combination therapy is not sufficiently effective, a rectal resection may be necessary. During this procedure, the sphincter muscle is removed, which is why a colostomy is created.

Radiochemotherapy

Anal canal carcinoma is primarily treated with combined chemoradiotherapy. This consists of radiation therapy over several weeks, accompanied by chemotherapy with 5-fluorouracil and mitomycin. The goal is to reduce the tumor size or achieve complete remission. Significant tumor regression is often observed within weeks of starting chemoradiotherapy.

In the Presence of Metastases

If metastases are already present, systemic therapies, radiation therapy, or local procedures are used, usually for palliative purposes. 

Anal cancer generally has a more favorable prognosis, particularly in the early stages. The 5-year survival rate is 70–90%. The tumor stage, lymph node involvement, and response to treatment are critical factors. Structured follow-up is necessary to detect recurrences early. It typically takes place every 3 months during the first two years.

Measures to prevent anal cancer focus on reducing key risk factors:

• HPV vaccination against high-risk types such as HPV 16
• Practicing safe sex
• Quitting smoking
• Treatment of inflammatory conditions in the anal area
• Strengthening the immune system