Anal Cancer

The anus is part of the gastrointestinal tract. It is the opening at the end of the large intestine, below the rectum, where bowel movements leave the body. Anal cancer begins when normal cells in or on the anus change and grow uncontrollably, forming a mass called a tumor. A tumor of the anus can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other areas of the body).

At first, the changes in a cell are abnormal, not cancerous. Researchers believe, however, that some of these abnormal changes are the first step in a series of slow changes that can lead to cancer. Some of the abnormal cells go away without treatment, but others can become cancerous. This phase of the disease is called dysplasia (an abnormal growth of cells). Dysplasia in the anus is called anal intraepithelial neoplasia (AIN) or anal squamous intraepithelial lesions (SILs). Growths—such as polyps or warts—that are not cancerous can also occur in or around the anus; some may become cancerous over time. In some cases, the precancerous tissue needs to be removed to keep cancer from developing.

The anus is made up of different types of cells, and each type can become cancerous. There are several different types of anal cancer based on the type of cell where the cancer began:

• Squamous cell carcinoma is the most common type of anal cancer. This cancer begins in the outer lining of the anal canal.
• Cloacogenic carcinoma accounts for about one-quarter of all anal cancers. This type of cancer arises between the outer part of the anus and the lower part of the rectum. Cloacogenic cell cancer likely starts from cells that are similar to squamous cell cancer, and it is treated similarly.
• Adenocarcinoma arises from the glands that make mucous located under the anal lining.
• Basal cell carcinoma is a type of skin cancer that can appear in the perianal (around the anus) skin.
• Melanoma begins in cells that produce pigment (color), found in the skin or anal lining.

Symptoms and Signs

People with anal cancer may experience the following symptoms or signs. Sometimes, people with anal cancer do not show any of these symptoms. Or, these symptoms may be caused by a medical condition that is not cancer. If you are concerned about a symptom or sign on this list, please talk with your doctor.   

• Bleeding from the anal area
• Pain or pressure in the anal area
• Itching or discharge from the anus
• A lump or swelling near the anus
• A change in bowel habits or change in the diameter of the stool

Stages and Grades

Staging is a way of describing where the cancer is located, if or where it has spread, and whether it is affecting other parts of the body. Doctors use diagnostic tests to determine the cancer’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient’s prognosis (chance of recovery). There are different stage descriptions for different types of cancers.

One tool that doctors use to describe the stage is the TNM system. TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:

• How large is the primary tumor and where is it located? (Tumor, T)
• Has the tumor spread to the lymph nodes? (Node, N)
• Has the cancer metastasized to other parts of the body? (Metastasis, M)

The results are combined to determine the stage of cancer for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.

Here are more details on each part of the TNM system for anal cancer:

Tumor. Using the TNM system, the "T" plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are also divided into smaller groups that help describe the tumor in even more detail. Specific tumor stage information is listed below:

TX: The primary tumor cannot be evaluated.

T0: There is no tumor.

Tis: Carcinoma in situ (early cancer that has not spread to other tissue) is present.

T1: The tumor is no larger than 2 centimeters (cm).

T2: The tumor is larger than 2 cm but not larger than 5 cm.

T3: The tumor is larger than 5 cm.

T4: The tumor has invaded other organs, such as the urethra, bladder, or a woman’s vagina.

Node. The “N” in the TNM staging system stands for lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes near the anus are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.

NX: Regional lymph nodes cannot be evaluated.

N0 (N plus zero): There is no regional lymph node metastasis.

N1: Cancer had spread to the perirectal (around the rectum) lymph nodes.

N2: Cancer has spread to the internal iliac (pelvic) and/or the inguinal (groin) lymph nodes on the same side of the body.

N3: Cancer had spread to the perirectal and inguinal lymph nodes and/or the internal iliac and/or inguinal lymph nodes on both sides of the body.

Distant metastasis. The “M” in the TNM system indicates whether the cancer has spread to other parts of the body.

MX: Distant metastasis cannot be evaluated.

M0 (M plus zero): There is no distant metastasis.

M1: There is metastasis to other parts of the body.

Cancer stage grouping

Doctors assign the stage of the cancer by combining the T, N, and M classifications.

Stage 0: Abnormal cells are in the first layer of the lining of the anus only. The abnormal cells may become cancer. This stage is also called carcinoma in situ (Tis, N0, M0).

Stage I: The tumor is no larger than 2 cm and has not spread to the lymph nodes or other parts of the body (T1, N0, M0).

Stage II: The tumor is larger than 2 cm and has not spread to the lymph nodes or other parts of the body (T2 or T3, N0, M0).

Stage IIIA: The tumor may be any size and has spread to either the nearby lymph nodes or to organs, such as the urethra, bladder, or a woman’s vagina (T1 or T2 or T3, N1, M0; or T4, N0, M0).

Stage IIIB: The tumor has invaded other nearby organs, but lymph node spread is limited to the area around the rectum; there is no distant spread. Or, the tumor may be of any size; lymph node spread can be local or distant, but there is no disease spread to distant organs (T4, N1, M0; or any T, N2 or N3, M0).

Stage IV: The tumor may be any size and has spread to the lymph nodes and to distant parts of the body (any T, any N, M1).

Recurrent: Recurrent cancer is cancer that has come back after treatment. If there is a recurrence, the cancer may need to be staged again (called re-staging) using the system above.

Grading

Histologic grade (G). In addition to the TNM system, doctors may also assign a histologic grade to the cancer. Histologic grade indicates how closely the cancer cells resemble normal tissue under a microscope. In general, the more differentiated the anal cancer tissue, the better the prognosis. A tumor's grade is described using the letter “G” and a number.

GX: The tumor grade cannot be identified.

G1: The cells look more like normal tissue cells (well differentiated).

G2: The cells are somewhat different from normal cells (moderately differentiated).

G3: The cells do not look like normal cells (poorly differentiated). 

G4: The cells barely resemble normal cells (undifferentiated).

Treatment

This section outlines treatments that are the standard of care (the best proven treatments available) for this specific type of cancer. When making treatment plan decisions, patients are also encouraged to consider clinical trials as an option. A clinical trial is a research study to test a new treatment to evaluate whether it is safe, effective, and possibly better than the standard treatment. Your doctor can help you review all treatment options. For more information, see theClinical Trials and Latest Research sections.

Treatment overview

In cancer care, different types of doctors often work together to create a patient’s overall treatment plan that combines different types of treatments. This is called a multidisciplinary team.

For anal cancer, there are three main types of treatment: surgery, radiation therapy, and chemotherapy. Descriptions of each treatment option are listed below. Treatment options and recommendations depend on several factors, including the type and stage of cancer, possible side effects, and the patient’s preferences and overall health. Take time to learn about your treatment options and be sure to ask questions about things that are unclear. Also, talk about the goals of each treatment with your doctor and what you can expect while receiving the treatment. Learn more about making treatment decisions.

Surgery

Surgery is the removal of the tumor and surrounding tissue during an operation. The type of surgery for anal cancer depends on the stage of the cancer. A surgical oncologist is a doctor who specializes in treating cancer using surgery. Surgery for anal cancer may also be performed by a colorectal surgeon, who specializes in surgery on the colon or rectum.

Anal carcinoma in situ or early-stage cancer can often be treated by removing the abnormal cells and a small area of the surrounding normal tissue (called a margin). Afterward, patients should receive regular follow-up screening to watch for and remove any new abnormal cells.

Previously, most patients with later stages of anal cancer were treated surgically before effective chemotherapy and radiation therapy were developed for anal cancer. However, studies have shown similar cure rates between surgical treatment and the combination of radiation therapy and chemotherapy. Now, most patients have a biopsy (which may require some level of surgery; see Diagnosis) followed by chemotherapy and radiation therapy without further surgery. Many patients can avoid major surgery with this type of combined treatment.

If a patient cannot have chemotherapy or radiation therapy, surgery may be recommended. Surgery may also be recommended if the cancer remains after initial treatment or returns after treatment has been completed. A persistent or recurring tumor may be treated with an abdominoperineal resection, which is the surgical removal of the anus, rectum, and part of the colon. This procedure results in acolostomy (an opening on the abdominal wall to allow feces to be collected in a bag). During this procedure, lymph nodes may also be removed (called a lymph node dissection).

Radiation therapy

Radiation therapy is the use of high-energy x-rays or other particles to kill cancer cells. A doctor who specializes in giving radiation therapy to treat cancer is called a radiation oncologist. The most common type of radiation treatment is called external-beam radiation therapy, which is radiation given from a machine outside the body. When radiation treatment is given using implants, it is called internal radiation therapy or brachytherapy. A radiation therapy regimen (schedule) usually consists of a specific number of treatments given over a set period of time. Radiation therapy for anal cancer is often combined with chemotherapy.

Patients with both anal cancer and HIV may be treated with lower doses of radiation therapy, depending on the degree to which the patient’s immune system is compromised by the HIV.

Side effects of radiation therapy may include fatigue, mild skin reactions, upset stomach, temporary anal irritation, loose bowel movements, and discomfort when having a bowel movement. Scar tissue may form from the damage to anal tissue, which may interfere with bowel function. Most side effects go away soon after treatment is finished.

Learn more about radiation therapy.

Chemotherapy

Chemotherapy is the use of drugs to kill cancer cells, usually by stopping the cancer cells’ ability to grow and divide. Systemic chemotherapy is delivered through the bloodstream to reach cancer cells throughout the body. Chemotherapy is given by a medical oncologist, a doctor who specializes in treating cancer with medication. A chemotherapy regimen (schedule) usually consists of a specific number of cycles given over a set period of time. A patient may receive one drug at a time or combinations of different drugs at the same time.  

Chemotherapy for anal cancer usually consists of a combination of drugs. The main chemotherapy drugs given for anal cancer are fluorouracil (5-FU, Adrucil) and mitomycin C (Mitozytrex, Mutamycin) or fluorouracil and cisplatin (Platinol). Chemotherapy is particularly effective for treating anal cancer when given in combination with radiation therapy. The combined treatment allows the use of lower radiation doses and improves the likelihood of completely destroying the tumor.

Patients with both anal cancer and HIV may receive lower doses of chemotherapy, depending on the degree to which the patient’s immune system is compromised by the HIV.

The side effects of chemotherapy depend on the individual and the dose used, but they can include fatigue, risk of infection, nausea and vomiting, hair loss, loss of appetite, and diarrhea. These side effects usually go away once treatment is finished.

Learn more about chemotherapy and preparing for treatment. The medications used to treat cancer are continually being evaluated. Talking with your doctor is often the best way to learn about the medications prescribed for you, their purpose, and their potential side effects or interactions with other medications. Learn more about your prescriptions by using searchable drug databases.

Getting care for symptoms and side effects

Cancer and its treatment often cause side effects. In addition to treatment to slow, stop, or eliminate the cancer, an important part of cancer care is relieving a person’s symptoms and side effects. This approach is called palliative or supportive care, and it includes supporting the patient with his or her physical, emotional, and social needs.

Palliative care can help a person at any stage of illness. People often receive treatment for the cancer and treatment to ease side effects at the same time. In fact, patients who receive both often have less severe symptoms, better quality of life, and report they are more satisfied with treatment.

Palliative treatments vary widely and often include medication, nutritional changes, relaxation techniques, and other therapies. You may also receive palliative treatments similar to those meant to eliminate the cancer, such as chemotherapy, surgery, and radiation therapy. Talk with your doctor about the goals of each treatment in your treatment plan.

Before treatment begins, talk with your health care team about the possible side effects of your specific treatment plan and supportive care options. And during and after treatment, be sure to tell your doctor or another health care team member if you are experiencing a problem so it is addressed as quickly as possible. Learn more about palliative care.   

Recurrent anal cancer

A remission is when cancer cannot be detected in the body and there are no symptoms. This may also be called “no evidence of disease” or NED. 

A remission can be temporary or permanent. This uncertainty leads to many survivors feeling worried or anxious that the cancer will come back. While many remissions are permanent, it’s important to talk with your doctor about the possibility of the cancer returning. Understanding the risk of recurrence and the treatment options may help you feel more prepared if the cancer does return. Learn more about coping with the fear of recurrence.

If the cancer does return after the original treatment, it is called recurrent cancer. It may come back in the same place (called a local recurrence), nearby (regional recurrence), or in another place (distant recurrence).

When this occurs, a cycle of testing will begin again to learn as much as possible about the recurrence, including whether the cancer’s stage has changed. After testing is done, you and your doctor will talk about your treatment options. Often the treatment plan will include the therapies described above (such as surgery, chemotherapy, and radiation therapy) but they may be used in a different combination or given at a different pace. Your doctor may also suggest clinical trials that are studying new ways to treat this type of recurrent cancer.

People with recurrent cancer often experience emotions such as disbelief or fear. Patients are encouraged to talk with their health care team about these feelings and ask about support services to help them cope. Learn more about dealing with cancer recurrence.

Metastatic anal cancer

If cancer has spread to another location in the body, it is called metastatic cancer.

Patients with this diagnosis are encouraged to talk with doctors who are experienced in treating this stage of cancer, because there can be different opinions about the best treatment plan. Learn more about seeking a second opinion before starting treatment, so you are comfortable with the treatment plan chosen. This discussion may include clinical trials.

Your health care team may recommend a treatment plan that includes a combination of surgery, radiation therapy, and chemotherapy. Supportive care will also be important to help relieve symptoms and side effects.

For most patients, a diagnosis of metastatic cancer is very stressful and, at times, difficult to bear. Patients and their families are encouraged to talk about the way they are feeling with doctors, nurses, social workers, or other members of the health care team. It may also be helpful to talk with other patients, including through a support group.