Radiation therapy is a common treatment used in conjunction with chemotherapy for anal cancer stages I-III. Here, we take a look at what radiation therapy for anal cancer consists of, when it is used and the main side effects.

What is radiation treatment for anal cancer?

Radiation for anal cancer involves using an external beam of radiation that is directed towards the cancer location to shrink tumors and kill cancer cells.

When is it used?

You are likely to have radiotherapy in combination with chemotherapy as your main form of treatment. For individuals with anal cancer stages I-III, radiation is typically 5 days a week for 5 to 6 weeks. Individuals with stage IV or recurrent cancer may receive radiation in locations where the cancer has spread.

How is radiation given?

There are different types of radiation for anal cancer treatment. The area receiving radiation is called the radiotherapy field. Your treatment team will aim to limit radiation only to the affected cancer cells, although healthy cells may be exposed to radiation too.

External-beam radiation therapy

External-beam radiation therapy (EBRT) is the most commonly used type of radiation for anal cancer. It focuses radiation from outside the body onto the cancer, much like an x-ray but with a much stronger dose.

Each session lasts only a few minutes and is itself usually painless. Typically, treatments take place on 5 days a week, for 5 to 7 weeks. This will vary depending on the type of EBRT and treatment need.

Newer techniques allow doctors to give higher doses of radiation to the cancer while reducing the radiation to nearby healthy tissues. Both of these require you to lie in very specific positions, so you may get a body mold made to help with this:

Intensity-modulated radiation therapy

Intensity-modulated radiation therapy (IMRT) is a version of three-dimensional conformal radiation therapy (3D-CRT). It is the preferred method of delivering external radiation for anal cancer. In IMRT, a computer-driven machine will rotate around you as it delivers radiation. Radiation beams can be shaped by the machine and delivered from different angles. The strength of radiation can also be adjusted. This can help limit the impact of radiation on nearby healthy cells and reduce side effects to some extent.

Stereotactic body radiation therapy

Stereotactic body radiation therapy (SBRT) might be used if anal cancer has come back (recurred) in the same place or nearby lymph nodes. It is also sometimes used when tumors have spread to other parts of the body (metastasized). It uses very focused beams of high-dose radiation given in 1 to 5 treatments.

Internal-beam radiation therapy

Also known as brachytherapy, this is not typically used in anal cancer. It involves placing small sources of radiation in or near the tumor. The purpose is to focus the radiation even more onto the cancer and minimize damage to healthy tissue.

Preparing for radiation treatment

Be sure to ask your medical team as many questions as you need to in order to feel as prepared as possible for your treatment. Your team will also guide you through a planning process that is designed to make you comfortable and ensure treatment effectiveness. This process may include radiation simulation to ensure you can find a comfortable position for treatment. You'll lie on the same type of table that's used during the actual therapy and your team will mark the area receiving therapy, with a marker or temporary tattoos, depending on your situation. You may also be fitted with a body cast to ensure you do not move during treatment.

Questions to ask the health care team (from Cancer.net)

  • Which health care professionals will I see at every treatment session?
  • Can you describe what my first session, or simulation, will be like?
  • Will I need any tests or scans before treatment begins?
  • Will my skin be marked as part of treatment planning?
  • Who can I talk with if I'm feeling anxious or upset about having this treatment?
  • How long will each treatment session take? How often will I have radiation therapy?
  • Can I bring someone with me to each session?
  • Are there special services for patients receiving radiation therapy, such as certain parking spaces or parking rates?
  • Who should I talk with about any side effects I experience?
  • Which lotions do you recommend for skin-related side effects? When should I apply it?
  • How else can I take care of myself during the treatment period?
  • Will special precautions be needed to protect my family and others from radiation exposure during my treatment period?
  • What will my follow-up care schedule be?

Side effects of radiation for anal cancer

Doctor showing patient something on a laptop


The area receiving the radiation is called the radiotherapy field. Your treatment team will aim to limit radiation only to the affected cancer cells, although healthy cells may be exposed to the same amount of radiation. The effects of radiation vary from person to person and it is difficult to predict the extent of your side effects. Side effects are also cumulative, and often get worse as treatment progresses. They can persist and even worsen for weeks after treatment has ended. Being aware of these possibilities is key to managing these effects and ensuring that your life after cancer is as healthy and happy as possible.

Diarrhea and irregular bowel function

Frequent bowel movements and even diarrhea are quite common after radiotherapy for anal cancer. Radiotherapy causes the anus and rectum to become irritated and inflamed, resulting in less effective ‘holding’ of the stool (poop). You may also experience bowel incontinence. This is often frustrating to experience in combination with sensitive skin around the anus, which makes bowel movements painful. Your treatment team may be able to prescribe painkillers as well as medication to reduce anal and rectal irritation. This usually calms down 2-3 weeks after treatment.

While many bowel issues related to radiation therapy tend to resolve with treatment completion, some effects can persist long term, and may not even appear until weeks to months after therapy has stopped. Please speak with your doctors for advice and suggestions on how to manage any bowel issues you experience.

Radiation enteritis

Radiation can cause what is known as radiation enteritis, or damage to the small intestine. Only 5-15% of people treated with radiation in the abdominal area will develop chronic enteritis. However, radiation effects can persist in a greater number of people for months to years after the completion of therapy before subsiding. Symptoms of enteritis include nausea, vomiting, watery diarrhea, and abdominal cramping. Longer-term symptoms include bloody diarrhea, a persistent feeling of needing to pass stool, weight loss and abdominal pain.

Radiation proctitis

In addition to enteritis, radiation may also cause damage to the rectum and anus resulting in something called proctitis. This is inflammation , which often causes rectal pain, bleeding, incontinence and discharge.

Changes to the skin

Red skin

Radiation treatment can cause sore, reddish skin at the treatment area, much like sunburn. Darkening of the skin, peeling, dryness and flaking are also common reactions. The severity of this reaction is very individual and hard to predict.

This reaction also comes on slowly – you won’t experience skin changes right away and the effects will be cumulative. Be aware that the ‘exit site’ of the radiation beam, i.e. the opposite side of your body from the treatment site, may become sore as well.

There are steps that can be taken to help soothe this side effect. Your team is best suited to give you advice on managing and preventing these skin reactions, and will let you know what types of creams or other topical treatments are acceptable to use during therapy. Let your radiation team know about the soreness you are experiencing. If it becomes too severe, they may decide to take a break from radiation for a few days to allow you to recover.

Memorial Sloan Kettering has some useful tips and tricks for managing the skin side effects of radiation for all cancers.

Given that the area affected by radiation includes the anus, you may experience difficulty and pain when passing stool. Your team may prescribe you painkillers to help manage these issues. Wearing loose clothing/underwear (boxers are great—for all genders!!) and using a soft cushion to sit on while you heal can also reduce the effects on this area.

Women may also experience vaginal irritation and discharge. Lubricating creams, moisturizers, and ointments can help ameliorate these effects. Speak to your nurse about these side effects so they can help get you relief faster.

Tiredness and fatigue

Radiation treatment may make you feel tired and weak. This is an effect of your body repairing the damage done to healthy cells. It is likely to creep up on you during the course of treatment, so even if you don’t feel tired at the beginning, you might by the end. This fatigue can persist for up to a few months after you have finished treatment.

Try and rest when you need to, but also strive to fit in light exercise into your day as well. Research has shown that regularly scheduling physical activity, including even short walks, can help manage symptoms of fatigue.

Tiredness and fatigue can persist for many months after you have concluded radiation therapy. It is important to keep your doctors informed of how you are feeling so they can monitor your body. This is also to make sure your tiredness is not being caused by other, more severe, problems. Keeping your doctors updated can also help them determine the best treatments for your fatigue. A journal detailing how you feel at certain times, and describing what you were doing around the time the fatigue starts may help determine which activities to avoid or limit.

Some suggested questions for your doctor are:

  • What is causing this fatigue?
  • Is there anything that can help me control my fatigue?
  • Can I exercise? What is a recommended amount?
  • Is there anything that I should NOT be doing?
  • Is there anything I can eat to give me more energy?
  • Is my tiredness normal?
  • How long will my fatigue last?
  • Where can I get some help and support?

Cancer Research UK has a great list of tips and tricks for managing fatigue related to cancer as an effect of radiation therapy, and fatigue caused by other cancer-related reasons as well.


Feeling sick is another side effect of radiation. Your treatment team may be able to prescribe medication to combat this, so be sure to speak with them. Nausea may impact your appetite, but it is imperative to continue drinking enough fluids throughout your treatment. Your doctor may recommend high-calorie meal replacement drinks to help ensure you are getting enough nutrition even if you feel you are unable to eat. These are easy to acquire without needing a prescription.

A certified oncology dietitian can also help with special dietary needs and restrictions that are a result of cancer and treatment side effects. Some cancer centers employ certified oncology dietitians, who typically see people only during treatment. They may have the acronym ‘CSO’ after their name. You can also ask your doctor or insurance provider for a referral. If referred to an outside dietitian, ask if they are aware of the specific needs of people undergoing cancer treatment.

Bladder irritation

Given its location, radiotherapy for anal cancer can affect the bladder as well. Your bladder may become irritated, making it feel as though you have an infection. This can lead to the sensation that you have to pass urine (pee) even if your bladder is empty. You may also feel pain when passing urine.

Drinking plenty of water will help alleviate symptoms, and cranberry juice has been known to help as well. Be sure to tell your doctor if the sensation persists after treatment has stopped, in case you actually do have an infection.

After I was finished I found the real recovery was just beginning. The effects of the radiation included stricture of the vaginal canal, unrelenting fatigue that lasted for over two years, and a medical community that was lacking in support and follow up of these issues.

I found a new gynecologist who specialized in oncological gynecology and through his PA who is female, found someone who understood my issues and was well versed in helping me. She did my first pelvic exam and instructed me on how to make intercourse less painful. This turned out to be not that difficult, and with her help and my own persistence, I soon returned to almost as good as new.

Lori D. (Stage I/II)

Anal stenosis

Many thrivers experience vaginal and anal stenosis (narrowing and/or loss of flexibility of the vaginal and anal passages) after treatment. For some, these changes begin during treatment. Stenosis means narrowing of the anal canal as a result of fibrosis and blood supply restriction to the tissues after radiation. It can result in constipation, painful bowel movements, rectal bleeding and narrow stools that break apart and are difficult to pass. Use of stool softeners and/or fiber supplements may help make bowel movements easier.

Your physician may be able to prescribe you dilators during treatment if you experience symptoms of stenosis. Some doctors integrate dilators into the radiation treatment program. In many cases, when dilators are prescribed or recommended, it is through a discussion with a member of the oncology nursing staff. Dilators may also be recommended once treatment has ended.

Damaged tissue can cause scar tissue to form in the anus and vagina. This can cause problems with functioning in these areas, especially when using the toilet or engaging in sexual activities.

Please see Dr. Jeanne Carter’s and Dr. Karyn Goodman’s presentations from the Foundation’s educational forum for more information on managing scar tissue and its effects.

Your doctor may refer you to a physical therapist who can work with you to slowly open the canal over time, including with the use of a dilator. This regimen may start with practitioner-assisted dilation followed by regular dilation by the patient. Daily dilation is possible, either digital (using the fingers) or mechanical (using a small dilator), in cases of mild or moderate stenosis. Speak with your care team about what may be best for you.

Physical therapy can also help maintain the openness of the anal canal. Physical therapists can help you with manual therapy, and possibly start you on a tailored dilator program.

Moderate to severe anal stenosis may require additional interventions. Please discuss your options with your care team if anal stenosis is affecting you.

Vaginal stenosis

Vaginal stenosis is a narrowing and shortening of the vagina, caused by buildup of scar tissue, drying and thinning of vaginal tissue, and a loss of vaginal lubrication. Vaginal stenosis is a common side effect for women who are being treated with chemoradiation. Contact often becomes painful, including during manual sexual stimulation and vaginal intercourse.

Many thrivers experience vaginal and anal stenosis after treatment. For some, these changes begin during treatment.

Vaginal stenosis can be managed through routine use of a dilator to stretch out the walls of the vagina. Vaginal moisturizers (which are different from lubricants) can help combat dryness and tightness in the vaginal area. These specially formulated preparations are typically applied at night and help improve conditions in vaginal skin by reducing itching, dryness and irritation. Lubrication aids are recommended when engaging in sexual activity.

Your physician may be able to prescribe you vaginal dilators during treatment if you are experiencing symptoms of stenosis. Your doctor may already integrate dilators into your radiation treatment program. In many cases, when dilators are prescribed or recommended, it is through a discussion with a member of the oncology nursing staff. Dilators may also be recommended once treatment has ended.

Clinicians who recommend dilators generally advise a series of dilators that start small and increase in size. This is to begin expanding the scar tissue. After a period of time, and consistent use of the dilators, vaginal manual stimulation and intercourse may become possible. Once you’re ready, clinicians recommend slowly initiating any penetrative intimate contact. People who are experiencing these side effects often explore other forms of sexual intimacy as well. Lubrication aides may be used to reduce friction during sexual activity. Vaginal moisturizers will help combat dryness over time. Speak with your doctor or nurse oncology team for recommendations.

As with anal stenosis, physical therapy is often helpful if you are experiencing vaginal stenosis. A practitioner may be able to help alleviate discomfort not only through manual therapy, but also by helping to get you on a personalized dilator program. Both physical and psychological improvements have been noted though the use of physical therapy for the pelvic floor, aiding vaginal and sexual issues related to radiation therapy for cancer treatment. Please speak with your care team for references and other advice about physical therapists.

Please see Dr. Jeanne Carter and Dr. Karyn Goodman’s presentations from our education forum on anal cancer treatment for more information on managing of vaginal stenosis and its effects.

In addition, please see our three-part series by Dr. Allison Palandrani, PT, DPT, on how physical therapy can help with anal cancer recovery. (Part two. Part three.) Also, see our update to this series which was posted August 26, 2020 on the blog.

Dr. Palandrani also presented at our educational forum, Living and Thriving After Treatment for Anal Cancer. View the full video. Dr. Palandrani’s presentation begins at 35:39.

Sex life and sexual performance

If your doctor clears you for sexual activity during treatment (and you want to have it!), note it is important to avoid becoming pregnant, or getting someone else pregnant, while undergoing radiation therapy. If these issues are of concern to you, refer to our section on Fertility below for information on preserving female and male fertility and why pregnancy must be avoided t.

Please see more information about taking care of your sexual health from our virtual anal cancer conference.

Erectile dysfunction

Radiation in the pelvic area can cause erectile dysfunction, although no one knows exactly why this occurs. It is possibly due to nerve damage, changes to blood flow or decreased testosterone. It IS known that greater doses of radiation received, and over larger areas, are correlated with a greater likelihood of experiencing sexual side effects.

Men who smoke, have a history of heart disease, diabetes or high blood pressure may also be at greater risk of experiencing erectile dysfunction as a result of radiation therapy. These conditions may have caused damage to the body, which is then exacerbated by the radiation.

Men also may experience some pain during ejaculation after undergoing radiation therapy, but this usually decreases and disappears as time goes on.

Macmillan Cancer Support has a resource section that discusses treatments to help you manage erectile dysfunction in greater depth. You can also speak with your physical therapist to explore the full range of options for erectile dysfunction treatment.


Radiation can affect fertility in both men and women, particularly given the location of radiation administered for anal cancer.

In men, radiation at high doses can kill sperm-producing stem cells and affect sperm production. Radiation can also affect the sperm itself—it’s therefore advised that men speak with their doctor before starting a pregnancy (or if they are at risk of starting one) during treatment.

In women, ovaries can become damaged during radiation therapy. The amount of radiation absorbed by the ovaries will determine fertility after treatment. High doses can destroy up to all of a woman’s eggs, resulting in total infertility or early menopause. One option to help preserve fertility is called ‘ovarian transposition’, which involves moving the ovaries out of the field of radiation. If, when the appropriate time comes, it is not possible to become pregnant naturally with the ovaries in this new spot, you may need to have them moved again, or look into in vitro fertilization (IVF). The decision to undertake this procedure depends on a variety of factors, inclusive of age, pregnancy desires, medical condition, and prognosis. Ask your team about the risks and benefits, as well as the feasibility of such a procedure.

If the uterus is affected by radiation, scarring may limit blood flow and flexibility. This can cause a pregnancy to be at a higher risk of miscarriage, low-birth weight, and premature delivery. As radiation can harm a growing fetus, it is critical to avoid becoming pregnant until treatment is complete. The American Cancer Society has listed a number of options that may be available to preserve your fertility. Speak with your doctor about ways to manage pregnancy and fertility, if these are issues that affect you.

Pelvic floor dysfunction

In women, the pelvic floor consists of the muscles and connective tissues that support the bladder, vagina, uterus, and rectum. In men, it is the supportive structures of the bladder, rectum and other pelvic organs. Everyone has nerves that carry signals from the brain to these organs.

Radiation therapies can cause damage or weakening of this pelvic region in both men and women.

Major side effects of radiation therapy to the pelvic region include:

  • Urinary dysfunction, including lack of bladder control that causes leakage.
  • Bowel dysfunction, causing stool leakage and incontinence.
  • Pelvic organ prolapse, a condition in which the vaginal walls protrude out of the vaginal opening.
  • Vaginal stenosis.
  • Anal stenosis.
  • Erectile dysfunction.

We explain these issues and their management in greater detail elsewhere on this page.

Managing pelvic floor dysfunction can take several forms:

  • Physical therapy can help you learn to relax your muscles and coordinate your movement in the pelvic floor area. See our three-part series on the benefits and function of physical therapy.
  • Behavioral changes may help. This could mean avoiding pushing or straining when using the toilet. Learning how to relax the pelvic floor muscles, and yoga and warm baths can help with relaxing this area.
  • Low-dose muscle relaxants may be prescribed, so speak to your medical team to see if this is a viable option for you.

Effects on the bones

Radiation often weakens the bones of the affected area, namely the pelvis and hips. This can increase the risk of fractures, particularly in older women and women who had symptoms of osteoporosis prior to treatment.

Managing bone weakening and associated complications include maintaining a healthy weight, as well as performing any type of weight-bearing physical activity (walking, dancing, climbing stairs, etc.). Speak with your doctor to help create an appropriate exercise plan based on your needs, abilities, and fitness level. This type of activity places stress on bones. It may seem counterintuitive to perform these exercises as an antidote to thinning bones, but the stress triggers your body to make more bone cells, encouraging growth. A physical therapist may be a good resource to help build a safe and effective program to counteract bone density decline. They can help you avoid placing excessive stress on vulnerable areas.

Calcium and vitamin D supplements can also be used. Make sure to consult with your physician team before beginning any supplement or exercise regimen.


Lymphedema, or swelling, may appear in the legs if radiation is given to lymph nodes in the groin. This swelling is caused by a buildup of lymph fluid in tissues that are right under the skin. Lymphedema caused by radiation can appear months to years after treatment is over, and can range from mild to severe and uncomfortable. This type of build-up can prevent cells from receiving proper nutrition, affect wound healing, and lead to infections.

Call your nurse or doctor if you start to notice any of the following signs of lymphedema:

  • Parts of your body such as the legs or genitals feeling full/heavy.
  • Your skin feels tight or hard or looks red.
  • New aching, tingling or discomfort in the radiation area that wasn’t there before.
  • Less movement or flexibility in joints near the radiation area.
  • Tighter clothes or accessories in a particular area, such as in one leg, even though you haven’t gained weight.

Swelling, soreness, tightness or redness could be a sign of an infection or blood clot and requires treatment right away. Be sure to call your doctor if you have a temperature of 100.5°F or more, or if you have a new pain in the area with an unknown cause.

Getting regular checkups, reporting changes, maintaining a healthy weight and getting enough exercise, with the guidance of a medical professional, are all recommended for people at risk of lymphedema. Compression garments can help prevent or reduce swelling and should also be used with professional guidance.

Physical therapy can help here, too. Therapists can determine atailored combination of manual and compression therapy, including lymphatic drainage. These techniques can promote fluid clearance and allow for more free and comfortable movement. There are physical therapists who specialize in alleviating lymphedema. Speak with your care team for more information. For a link to a pelvic floor therapist, please see our Medical Resources page.

Finally, the American Cancer Society also has a useful document on understanding and managing lymphedema.

During treatment

Diet during treatment

Toast bananas

In general, the recommended diet is bland and low-fiber. One specific diet recommended is the BRAT (Bananas, Rice, Applesauce, Toast) diet. Ask your doctor about the specifics, and if this diet is right for you. Your doctor may be able to refer you to a dietitian specializing in gastrointestinal issues to look into options with you further.

Recommendations from the National Cancer Institute include the following:

  • A lactose-restricted diet. Damage to the intestines can result in the loss of essential enzymes needed to digest milk and dairy products that are not lactose-free.
  • Adjust your fiber consumption. A lower fiber diet may help reduce symptoms during this time.
  • Avoid caffeine.
  • Avoid fatty, rich foods.
  • Avoid fresh and dried fruits and vegetables.
  • Avoid whole-grain breads and cereals.
  • Avoid strong spices and herbs.
  • Avoid prune juice.

Additionally, please see this helpful presentation by a dietitian on a panel discussion facilitated by the Foundation at the International Anal Neoplasia Society. It includes advice for nutrition during and after treatment.

Other management solutions for gastrointestinal complaints resulting from radiation therapy may include the use of probiotics, oral steroids and bowel rest:

  • Probiotics are supplements that contain beneficial microorganisms that help modify gut microflora to improve conditions such as diarrhea induced by radiation and its effects.
  • Steroids can be used as anti-inflammatory agents, helping to reduce pain and discomfort.
  • Bowel rest basically means resetting your diet temporarily: you will start with a few days of clear liquids and gradually add back soft foods. A more normal diet is resumed over a period of a few weeks.

It may be helpful to keep a food journal, inclusive of how food has been prepared and your reaction to it, in order to determine what you can and cannot tolerate.

Finally, some thrivers find that using adult diapers or pads can help manage some of the symptoms of radiation proctitis, such as bowel incontinence or rectal bleeding.

If diarrhea occurs, your treatment team can prescribe medication to help manage it. It is extremely important to stay very hydrated. Diet also has an impact on bowel movements. A low fiber diet may also help lower the frequency of diarrhea episodes.

Coping with side effects

In addition to your medical team, who take care of your diagnosis, medications and treatments, we have found that thrivers benefit from seeking out a range of other specialists to help them through their cancer and recovery. Your medical care team may not know or share all of these suggestions with you, and you may not actually need all of these services. Unfortunately, there is not yet a standard protocol for creating a care team after anal cancer treatment.

However, through our conversations with thrivers and medical providers at different institutions, we have found that these specialists can help improve an anal cancer thriver’s quality of life after treatment. It is best to find people within these specialties who have additional certification in oncology or have worked with cancer patients before. Some cancer centers employ these professionals on-site. Discuss the best options with your medical team.

Physical therapy

Physical therapist

Pelvic floor physiotherapy can help with a range of side effects from radiation, such as pain, fatigue, lymphedema and pelvic floor dysfunction. Find a provider on Pelvic Pain Society and on APTA Pelvic Health.


Dietitians can help you design an eating plan that you can tolerate during and after treatment, and that still provides you the best nutrition during this time. Some cancer centers employ certified oncology dietitians who may have the acronym ‘CSO’ after their name. You can also ask your doctor or insurance provider for a referral.

Sex therapy

Intimacy may become more difficult, or take a different form during and after treatment for anal cancer. A sex therapist who specializes in working with cancer patients will help you rediscover sex after a cancer diagnosis.

You can find out more about the type of work these specialists do and the side effects they help to mitigate through our educational forums:

Dr. Jeanne Carter, Head of Female Sexual Medicine and Women’s Health programs: Long-Term Side-Effects After Treatment for Anal Cancer

Dr. Allison Palandrani, Branch Director, Pelvic Health and Rehabilitation Center: Physical Therapy After Treatment for Anal Cancer (a three-part series)

Connect with a Peer

Looking for someone to talk to about your anal cancer diagnosis? We are here to help. The Peer to Peer Support Program is a free service provided by the Anal Cancer Foundation that matches anal cancer thrivers (our word for survivors) and caregivers with thriver volunteers and caregiver volunteers.