Radiation therapy is the most common treatment for anal cancer. It can be used with chemotherapy. It also is used after surgery, to kill the rest of the cancer cells. MSK experts use advanced methods to deliver exact doses of radiation directly to tumors. Our methods cause less harm to nearby healthy tissues.

Radiation oncologists are experts in treating cancer with radiation. MSK’s radiation oncologists are some of the most experienced in the country. Our care team includes radiation oncologists, nurses, therapists, physicists, and surgeons. Together we make sure you get the safest treatment and support services to help you keep your quality of life.

Types of Radiation for Anal Cancer

This information explains the most common types of radiation used to treat anal cancer.

Intensity-Modulated Radiation Therapy for Anal Cancer

Intensity-modulated radiation therapy (IMRT) is the most common radiation treatment for anal cancer. This form of external-beam radiation delivers high doses of radiation to the tumor without harming healthy tissue. It uses advanced computer software and CT scans to mold radiation doses to the shape of the tumor. MSK experts treat among the highest number of patients in the country with radiation for anal-rectal cancer.

Before treatment, radiation oncologists and medical physicists will get information about the treatment area. You will have imaging tests, such as:

• Computed tomography (CT) scan. During a CT scan, a special machine uses X-rays to take a fast series of computerized pictures from different angles. These detailed 3D images will map the tumor.
• Magnetic resonance imaging (MRI). An MRI is a test that uses strong magnetic fields to take pictures. These detailed images are used to identify the outline of the tumor.
• Positron Emission Tomography (PET) scan. A PET scan takes detailed, computerized pictures used to map the outline of the tumor.

Your care team will enter the information from your tests into computer software to plan your treatment. It tells us how to position the radiation beams so we can target the tumor with exact doses of radiation. You may also get chemotherapy to weaken the cancer cells before radiation treatment.

Side Effects of Radiation Therapy for Anal Cancer

You may get side effects from radiation right away, such as:

• Diarrhea and pain while going to the bathroom.
• Burns or rashes on the skin at the treatment site.
• Feeling tired.
• Nausea (feeling like throwing up).
• Irritation of the vagina.

Radiation oncologists are experts in treating cancer with radiation. They will talk with you about what to expect after radiation. They will tell you when side effects are likely to start. We can prescribe items to keep you as comfortable as possible. Examples are a topical cream (medication applied to skin) or pain medication.

Most side effects go away when treatment ends. You can have other side effects that last longer. To help with them, our experts developed methods and support programs.

• Fertility: Radiation can affect the fertility (ability to have a pregnancy) of men and women. Our experts know that fertility is an important and very personal concern. We can help give you the best chance of preserving (keeping) your fertility. Learn more about how to preserve fertility.
• Health of the vagina: Radiation for anal cancer can harm the vagina. You can have discomfort and pain. MSK has a program to help you keep your vaginal and sexual health before, during, and after treatment. Your care team can offer special tools during radiation that can help protect your vagina. Learn more about sexual health services.
• Bowel function: Radiation to the anus can harm tissue in your bowel (small and large intestines). Over time, this can cause scar tissue to form. This scar tissue can affect the muscles that control the anus. You may not have the same control over your bowel actions (being able to poop). Your care team can offer special tools or treatments to reduce or adapt to changes in bowel action.
• Pelvic floor health: Cancer and its treatment can harm the muscular floor of the pelvis. This can cause pain in your lower back area. It also can cause incontinence, which is leakage of urine (pee) or stool (poop) that you can’t control. It also can make it harder for you to enjoy sexual relations. Physical therapists identify the problem and create a treatment plan for it. Treatment includes hands-on methods to help muscle imbalances, and exercises to help muscle strength and coordination.