Understanding Radiation Therapy and its Side Effects

by Celia Chen  MScPT
Registered Physiotherapist
updated July 31, 2025

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If you’re about to start radiation therapy or are already undergoing radiation therapy, you probably have some questions and concerns about what to expect. Radiation therapy is a powerful cancer treatment. It can shrink tumours, kill cancer cells and most importantly, improve your prognosis. However, like all cancer treatments, it comes with side effects.

Let’s go through the different types of side effects, when they might happen, how long they might last, how they can impact your body, and how physiotherapy can support you through this process.

 

What is radiation therapy?

Radiation therapy is a common cancer treatment that uses high energy x-rays, gamma rays, or charged particles to shrink tumours and destroy cancer cells. It can be used to treat both primary tumours (at the original site) and secondary tumours (metastases). It is a local treatment, meaning it affects only the specific area being targeted.

It works by damaging the DNA of cancer cells, creating oxidative stress, which interferes with their ability to grow and divide. Since cancer cells cannot repair themselves between treatments, they eventually die. Normal cells are usually able to repair and regenerate between sessions, however, some healthy tissue in the radiation field may still be damaged and not fully recover.

 

When can radiation therapy be used?

Neoadjuvant Radiation: this is given BEFORE surgery to shrink the tumour and make removal easier

Adjuvant Radiation: this is given AFTER surgery to destroy any remaining cancer cells and reduce the risk of recurrence. This is one of the most common uses, especially for pelvic cancers.

Palliative Radiation: this is usually delivered at lower doses to shrink tumours, slow their growth and manage tumour burden and side effects. With advances in therapy, many people are living longer with stage 4 cancer, and are often using low dose palliative radiation as part of their care.

 

Types of radiation therapy

External Beam Radiation Therapy (EBRT): this is the most common type. It uses a machine that sends high energy beams from outside your body to the area where the cancer is.

• It is non-invasive
• The beams are aimed at your tumour using small tattoo like marks on your skin to help with accurate targeting every session
• Treatment is given in short daily sessions that usually last 5-10 minutes over 4-6 weeks
• While it targets cancer cells, some healthy tissues nearby may also be affected, which can cause side effects depending on the area being treated

Internal Radiation Therapy (Brachytherapy): this type delivers radiation from inside your body, placing small seeds, ribbons, wires or applicators directly into or next to the cancer.

• These may stay in place for a few hours, days or permanently, depending on your treatment plan
• It is most commonly used to treat prostate and cervical cancers
• Because the radiation is placed right at the tumour, it causes less impact to nearby healthy cells, therefore, fewer side effects compared to EBRT.

Precautions specific to brachytherapy: if you’ve received seed implants (commonly used for prostate cancer), a small amount of radiation remains in your body for a period of time. While the risk to others is low, it’s important to follow these precautions:

• Avoid close physical contact with pregnant people and young children for the first few weeks, especially sitting on your lap or being close to your pelvic area as this is when radiation levels are highest
• Strain your urine for the first 7-10 days. This is to catch any radioactive seeds that may pass out of your body by accident
• Use a condom for penetrative sex in the first few weeks. This helps to prevent any accidental release of seeds and minimizes exposure to your partner

 

Common side effects of radiation therapy

Side effects vary greatly from person to person and depend on factors like:

• Where on the body the radiation is directed
• Type of radiation, how much radiation is given and for how long. The total amount of radiation delivered to tissues can add up over the course of treatment. Higher doses or repeated treatments can increase the risk and severity of side effects, especially fibrosis or scarring
• Your general health and any other treatments or medications you’re receiving

Some side effects appear right away, while others may show up months or even years later. Some effects resolve over time, whereas other may become permanent. It is important to understand these side effects because early management can prevent long term problems.

 

Common short-term side effects (during or soon after treatment)

Energy and Wellbeing:

• Fatigue: often starts around week 1-4. Staying active can help manage this
• Sleep, appetite, or mood changes including anxiety or depression
• Immunosuppression: temporary increased risk of infections

Skin and Hair:

• Skin changes (radiation dermatitis): redness, peeling, dryness, blistering, or sores in the treated area. Usually starts within 90 days of radiation exposure.
• Hair loss: usually only in the area being treated

Mouth, Throat and Digestive Tract:

• Dry mouth, mouth sores, difficulty swallowing. This is common in head, neck or chest radiation
• Changes in taste or smell
• Digestive issues such as nausea, vomiting, diarrhea, constipation, especially with abdominal or pelvic radiation

Bladder and Bowel

• Bladder irritation: urgency, frequency, pain or burning with voiding
• Bowel irritation: pain with bowel movements, loose stools

Sexual Health

• Sexual dysfunction: low libido, pain with vaginal or anal penetration, vaginal dryness or general discomfort during intimacy. These may persist into long term if not addressed

Other Short-term effects:

• Edema (swelling)
• Delayed wound healing
• Lowered immunity: increased risk of infections

 

Common long term side effects (months or years after treatment)

Tissue Changes

• Radiation fibrosis: this is scarring or stiffening of soft tissues like muscles, ligaments, skin and blood vessels. This can start at onset of treatment but can persist lifelong. This causes muscle tightness or shortening, joint stiffness, reduced flexibility, decreased circulation or lymph flow. Our physiotherapists can help reduce this impact by providing manual therapy to release the tight muscles and teaching you exercises and stretches to continue with at home to improve your mobility.
• Chronic skin changes: thinning skin, fragile skin and development of visible blood vessels (telangiectasias)

Lymphatic System

• Lymphedema: fluid buildup due to lymphatic drainage issues. Common to have swelling in arms after breast cancer radiation treatment or legs after pelvic radiation. Our physiotherapists can help with this!

Nerves and Bone

• Neuropathy including radiation induced plexopathy: pain, weakness or numbness in the arms or legs
• Osteonecrosis: bone damage, commonly in the hip or jaw

Bladder and Bowel Function:

• Radiation Cystitis: inflammation of the bladder which can cause pain, urgency, frequency or blood in the urine
• Radiation Colitis: inflammation of the bowel which can cause pain, mucous or blood in stool and diarrhea
• Fecal incontinence or bowel urgency
• Rare complications such as bowel perforation
• Stenosis (narrowing):
  – Bladder or urethral stenosis: difficulty urinating or incontinence
  – Rectal stenosis: difficulty with bowel movements
• Our pelvic health team commonly help patients with incontinence, bowel urgency and stenosis. They can help you to manage and improve these side effects and thus improve your quality of life! We also have registered dietitians on our team that can help with all the gut-related changes that can happen, such as food sensitivities, digestive issues, and ensuring proper nutrient absorption. You don’t have to live with these side effects long term.

Sexual and Reproductive Health

• Persistent sexual dysfunction: pelvic pain, painful intercourse, or vaginal dryness
• Vaginal stenosis: narrowing or scarring of vaginal tissue, may affect comfort during intercourse or medical exams. This can be managed with guidance from our pelvic team and the use of vaginal dilators, which we will teach you how to use safely and effectively.
• Early menopause and bone density loss (especially with pelvic radiation). Our pelvic team and registered dietitians can help with some of the changes here that can improve quality of life.
• Loss of fertility: due to radiation effects on reproductive organs

Daily Life Impact

• Decreased range of motion: radiation to the pelvic or hip region may reduce flexibility and mobility, particularly affecting the hip rotator and extensor muscles
• Decreased participation in activities of daily living, impacts work, social life, and intimacy due to ongoing symptoms
• Reduced quality of life if side effects are unmanaged – but support is available. We are here to help you live your best life!

 

How physiotherapy can help reduce these side effects and improve your quality of life

• Maintain flexibility and mobility: Regular movement and stretching exercises help prevent or reduce fibrosis and joint stiffness
• Pain relief: postural training, strengthening, and manual therapy can ease discomfort from tissue tightening
• Pelvic floor rehab to manage bladder, bowel and sexual health
• Dilator therapy to manage and prevent vaginal stenosis
• Lymphedema management (manual lymphatic drainage, scar tissue mobilization, and exercise)
• Mental health support to help cope with emotional impacts and helping you stay active and independent

 

Tips to minimize side effects

• Avoid wearing tight clothing and wear loose, comfortable clothing over the treated area (skirts, dresses, boxers)
• Avoid heating pads or ice packs over the radiated area as there can be nerve damage impacting sensation
• Use mild soap and lukewarm water when caring for sensitive skin
• Cover your skin from the sun and use SPF to protect your skin from sun exposure
• Avoid applying powders, perfumes, deodorants, oils, ointments or creams unless approved by your medical team
• Avoid scratching, scrubbing or rubbing irritated skin
• Stay active and keep moving as tolerated – movement helps circulation and reduce stiffness
• Discuss any symptoms with your healthcare team early;  this can prevent complications

 

Radiation therapy can cause many side effects but proper management and support can greatly improve your quality of life. Not everyone will experience all these side effects and many are manageable. Our team will guide you through what to expect and how to manage any changes during and after your treatment.