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Anal cancer treatments

The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on September 8, 2021.

Once you have been diagnosed with anal cancer, your multidisciplinary care team will work with you to customize a comprehensive treatment plan for your needs. Your individualized plan will include evidence-based medical treatments and technologies, as well as supportive care services designed to help you manage side effects.

Treating anal cancer requires the expertise of experienced doctors and surgeons. During treatment, you may encounter multiple types of doctors with various specialties on your care team, including:

  • Surgical oncologist, who treats cancer by performing surgery
  • Radiation oncologist, who treats cancer using radiation therapy 
  • Medical oncologist, who treats cancer using drugs such as chemotherapy
  • Colorectal surgeon, who performs surgery to treat diseases of the colon, rectum and anus

As a group, your care team is capable of recommending a comprehensive treatment plan. Many other medical professionals may play a role in your cancer care along the way as well, including nurses, pharmacists, oncology dietitians and social workers.

In the past, surgery was the only treatment for anal cancer, but today, the disease is often treated with a combination of radiation therapy and chemotherapy. Surgery remains an option for early-stage anal cancer, particularly stage 0, and some stage 1 and 2 anal cancers.

Typically, two surgical procedures are used to treat anal cancer, depending on the type and location of the tumor:

  • A local resection treats cancers in the lower part of the anal canal, known as the anal margin. This may be an option for early-stage anal cancer that has not spread. This approach is primarily used to remove small tumors not involving the sphincter, which is the muscle used to control bowel movements. The tumor is removed along with a small amount of surrounding tissue. The sphincter is left intact to allow for normal bowel movements after surgery. Chemotherapy and radiation therapy may follow surgery. Local resection may be all that is needed to treat stage 0 anal cancer. For stage 1 and 2 anal cancers that can be successfully removed by a local resection, chemotherapy and radiation therapy may be used after surgery. Local resection is used to treat anal cancer only when the tumor hasn’t grown into or near the anal sphincter. When anal cancer involves the sphincter, removing the tumor could damage this muscle and cause a loss of control of bowel movements.
  • An abdominoperineal resection is an option for recurrent cancer or cancer that has not responded to other treatments. It involves removing the anus and anal sphincter. Incisions are made in the abdomen and around the anus to remove the anus and rectum. A new opening is created to allow stool to pass from the body. A lymph node dissection to remove lymph nodes in the groins may also be performed, though this procedure may be done later. Abdominoperineal resection is an option for recurrent anal cancer (cancer that returns after treatment ends) or for stage 1 , 2 or 3 anal cancer that was unsuccessfully treated with other approaches.

Pain is a common side effect of surgery, but your care team can prescribe medicines to manage it.

In general, the potential complications of surgery include:

  • Excessive bleeding
  • Blood clots
  • Infection

Other side effects and complications depend on what type of procedure is performed.

Abdominoperineal resection is a more extensive surgery than local resection and comes with a higher risk of complications and side effects and a longer recovery time. Some of the risks and side effects of abdominoperineal resection include:

  • Digestive issues due to scar tissue forming in the abdomen
  • Urinating difficulties caused by damage in the urinary tract, which may require more surgery to fix
  • Erectile dysfunction or other sexual problems in men
  • Pain during sex for women

After an abdominoperineal resection, patients need a permanent colostomy bag to collect waste through an opening (stoma) in the abdomen.

Radiation therapy

Radiation therapy, in the form of X-rays or particles, is used to kill cancer cells.

Radiation therapy may be used in many different ways as a part of cancer treatment. For anal cancer, it’s most commonly combined with chemotherapy.

The combination of chemotherapy and radiation therapy given simultaneously is called chemoradiation. Chemoradiation is a common treatment option for an anal tumor that your care team is unable to remove with local resection because it’s grown too near the anal sphincter.

For anal cancer, the process of chemoradiation usually lasts five to seven weeks. Often, during the first week and the fifth week, you’ll be given a dose of intravenous (IV) chemotherapy drugs. At the same time, you’ll receive daily treatment with external beam radiation therapy (EBRT), five days per week, during the entire treatment period. Chemoradiation exposes patients to less radiation and is more likely to rid patients of the cancer than radiation therapy alone.

Doctors may recommend chemoradiation for stage 1, 2 or 3 anal cancer.

In other cases, radiation therapy alone may be used after surgery to help ensure that no cancer is left behind, or to help relieve symptoms of advanced anal cancer that has spread to another area and is causing pain or other problems.

For anal cancer, radiation therapy is most often delivered externally with external beam radiation therapy. This involves a machine outside your body that sends radiation toward the area of cancer. There are different types of EBRT that may be used to treat anal cancer, including:

  • Intensity-modulated radiation therapy (IMRT): For anal cancer, IMRT is the most common method of radiation therapy used. IMRT is a method of external beam radiation therapy that uses a specialized machine that rotates around you. As the machine turns, it sends beams of radiation into the body. The device can alter the shape, aim and intensity of the rays, allowing for more precise and safe delivery of radiation therapy.
  • Three-dimensional conformal radiation therapy (3D-CRT): This method of external beam radiation therapy uses specialized computers to target the cancer precisely. The computers create a detailed map of the tumor’s location then form multiple beams of radiation that target the tumor from different angles. The accuracy of the beams makes this approach less damaging to healthy tissue than some other methods of radiation therapy. The process typically requires you to have a plastic mold of your body created. During the procedure, you’ll need to wear this plastic body cast to prevent any movement from disrupting the accuracy of the radiation beams.
  • Stereotactic body radiation therapy (SBRT): This method of external beam radiation therapy may be used to treat a local or regional recurrence of anal cancer. Other times, it may be an option to help treat metastatic anal cancer that has spread to specific other parts of the body. The process of SBRT involves a high dose of radiation delivered in only a couple of sessions, compared with other methods that involve daily, low-dose radiation given over several weeks. During the treatment, you may be placed in a plastic body mold to prevent movement while high-dose radiation beams target the tumor from different directions. In total, you may receive one to five of these treatments.

Most side effects of radiation therapy are related to the area treated. For anal cancer, common side effects may include:

  • Diarrhea
  • Redness, blistering or other skin changes at the treatment site
  • Irritation and pain in or around the anus
  • Fatigue
  • Stomach upset
  • Bowel movement changes
  • Vaginal pain and discharge

These types of side effects tend to resolve after treatment ends, but there are also potential long-term effects of radiation therapy for anal cancer, including:

  • Bowel movement changes caused by damage to the anal sphincter
  • Pelvic or hip fractures due to weakened bones
  • Rectal bleeding and pain caused by damaged blood vessels
  • Infertility
  • Vaginal dryness and painful sex for women
  • Erectile dysfunction

Before undergoing radiation therapy for anal cancer, ask your doctor about the potential side effects and risks. In particular, if the possibility of infertility is concerning to you, it’s important to express that to your care team so they may ensure your treatment plan is suited to your preferences.

A combination of radiation and chemotherapy, mainly performed for anal preservation, may be recommended as an alternative to surgery that results in a permanent colostomy, which requires a bag attached to the abdomen to collect stool.

Chemotherapy drugs, given intravenously or orally, target cancer cells to destroy them or impede their ability to grow and reproduce, while radiation therapy allows radiation oncologists to target difficult-to-reach tumors. Higher doses of radiation may be directed at anal cancer cells while reducing exposure to healthy tissue.

Chemotherapy

Chemotherapy is a cancer treatment that involves using drugs, typically delivered into a vein or through a pill, to kill cancer cells or prevent them from spreading.

There are different ways chemotherapy is used to treat anal cancer, but, in most cases, it is combined with radiation therapy (chemoradiation). Chemoradiation is a primary treatment option for stage 1, 2 or 3 anal cancers that local resection cannot remove. The tumors eligible for chemoradiation have grown too near to the anal sphincter to be surgically removed without damaging the sphincter. Surgery may be used after chemoradiation, but sometimes chemoradiation on its own is used to treat anal cancer.

In other cases, your care team may recommend chemoradiation after surgery to help kill off any remaining cancer cells or for recurrent or metastatic anal cancer. Recurrent anal cancer may be treated with chemotherapy or radiation therapy if the recurrence is located in lymph nodes near the anus (regional recurrence). For metastatic anal cancer that has spread to other parts of the body, chemotherapy may help alleviate symptoms and prevent cancer cells from spreading further.

In general, chemotherapy comes with a risk of side effects such as:

  • Stomach upset
  • Poor appetite
  • Weight loss
  • Hair loss
  • Diarrhea
  • Sores in the mouth

Patients undergoing chemotherapy may also be more at risk of infections and experience frequent bruising, excessive tiredness and difficulty breathing. These symptoms stem from chemotherapy drugs affecting your body’s ability to make adequate amounts of blood cells.

It’s important to communicate openly about any side effects you experience while undergoing chemotherapy. Doctors have many ways to help relieve symptoms, but they need to know how you feel so they can help.

Immunotherapy

Immunotherapy is an approach to treating cancer that uses drugs to help the immune system locate and kill cancer cells efficiently.

Immune checkpoint inhibitors are one class of immunotherapy drugs that may help treat some anal cancers. These drugs stimulate your immune system by targeting specific proteins on immune cells and increasing their ability to attack cancer cells. Below are some of the immune checkpoint inhibitor drugs that may help treat some instances of anal cancer.

Opdivo® (nivolumab) and Keytruda® (pembrolizumab): These drugs may be an option for metastatic (stage 4) anal cancer in patients who have already undergone chemotherapy unsuccessfully. These drugs are delivered into a vein using an IV line every two or four weeks (for nivolumab) or every three or six weeks (for pembrolizumab).

Some of the more common side effects of immune checkpoint inhibitors include:

  • Tiredness
  • Upset stomach
  • Poor appetite
  • Cough
  • Bowel movement changes
  • Joint pain

These drugs may also cause more severe complications, including:

  • Fever, chills, facial flushing, rash, dizziness and difficulty breathing, which may be signs of an allergic reaction to the drugs.
  • Organ damage resulting from an autoimmune reaction, in which your immune system starts to attack healthy parts of the body. Autoimmune reactions are severe and may even be life-threatening if not reported and treated. Doctors can help stop these reactions by discontinuing treatment and prescribing drugs that help subdue the immune system’s response.

Treatment options by stage

The stage of anal cancer, which describes where the cancer is located and how far it’s spread, is one of the main factors in determining treatment. Below are the common treatment options for anal cancer, depending on the stage.

  • Stage 0 (cells are considered precancer and are limited to just the inner lining of the anus)
    • Local resection
  • Stage 1 and stage 2 (cancer has invaded the deeper layers of the anal wall but has not spread any further)
    • Local resection for tumors smaller than 2 cm that don’t affect the sphincter, potentially followed by chemoradiation
    • Chemoradiation for tumors that can’t be treated with local resection
    • Abdominoperineal resection for cancers that don’t respond to other treatments or recur after treatment
  • Stage 3 (cancer has invaded nearby organs or lymph nodes but hasn’t spread further)
    • Chemoradiation
    • Radiation therapy
    • Abdominoperineal resection for cancers that don’t respond to other treatments or recur after treatment
  • Stage 4 (cancer has become widespread in the body, invading distant organs)
    • Palliative treatments to relieve symptoms (including surgery, radiation therapy, chemotherapy or chemoradiation)
    • A clinical trial of immunotherapy (for cancers that haven’t responded to other treatments)

Recurrent anal cancer

After treatment has concluded, anal cancer sometimes comes back, which is known as recurrent anal cancer. The recurrence may take place in or near the anus (local recurrence) or in a different part of the body (distant recurrence).

Anal cancer that recurs locally is treated using a different therapy or combination of therapies than were used to treat the initial cancer. For example, those who undergo chemoradiation to treat the original cancer may have surgery (abdominoperineal resection) to treat a recurrence.

Anal cancer that recurs in organs or tissues far away from the anus are typically treated with chemotherapy. However, the goal may be to control the cancer’s growth and alleviate symptoms. Other options include surgery and radiation therapy.

Clinical trials

For some patients, particularly those who have exhausted other options or have advanced-stage or recurrent anal cancer, clinical trials may be beneficial. Advanced and recurrent anal cancer may be difficult to treat using the standard therapies, and enrolling in a clinical trial may provide more options. For stage 4 and recurrent anal cancer, the National Cancer Institute lists clinical trials testing immunotherapy and other novel approaches as a primary treatment option.

Next topic: What are the facts about anal cancer?

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