Radiation Therapy: How It Works, Side Effects & Recovery

What Is Radiation Therapy and How Does It Work?

Radiation therapy uses high-energy ionizing radiation to damage the DNA of cancer cells, preventing them from dividing and causing them to die. The treatment targets specific areas of the body where cancer is present, and approximately 50% of all cancer patients receive radiation therapy at some point during their treatment.

Radiation therapy, also known as radiotherapy, is a cornerstone of cancer treatment that has been used for over a century. The treatment works by delivering concentrated doses of high-energy radiation to cancer cells, causing irreparable damage to their genetic material (DNA). When cancer cells attempt to divide and replicate, the DNA damage prevents successful cell division, ultimately leading to cell death.

The fundamental principle behind radiation therapy lies in the difference between cancer cells and healthy cells. While radiation damages both types of cells, healthy cells have superior DNA repair mechanisms and can recover from radiation damage more effectively than cancer cells. This differential sensitivity is what makes radiation therapy an effective cancer treatment – it exploits the vulnerability of rapidly dividing cancer cells while allowing normal tissues to heal.

Modern radiation therapy has evolved significantly from its early days. Today's treatments use sophisticated computer planning systems, advanced imaging technologies, and precision delivery mechanisms to target tumors with remarkable accuracy. This precision allows doctors to deliver higher doses of radiation to the tumor while minimizing exposure to surrounding healthy tissues, resulting in better outcomes and fewer side effects.

The Science Behind Radiation Damage

Ionizing radiation produces its effects through two primary mechanisms. Direct damage occurs when radiation particles directly strike DNA molecules, breaking the chemical bonds that hold the DNA strands together. Indirect damage, which accounts for the majority of radiation effects, happens when radiation interacts with water molecules in cells, producing highly reactive free radicals that then damage DNA and other cellular structures.

The extent of damage depends on several factors, including the total radiation dose, the rate at which it's delivered, the type of radiation used, and the inherent sensitivity of the target tissue. Cancer cells, particularly those dividing rapidly, are generally more susceptible to radiation damage because they have less time to repair DNA damage before the next cell division.

Types of Radiation Used in Treatment

Several types of ionizing radiation are used in cancer treatment, each with unique properties that make them suitable for different clinical situations. The most common types include photon radiation (X-rays and gamma rays), electron beams, and particle therapy using protons or heavier ions.

Photon radiation, particularly high-energy X-rays generated by linear accelerators, is the most widely used form of radiation therapy. These beams can penetrate deep into the body, making them suitable for treating tumors located internally. The radiation dose is highest near the skin surface and gradually decreases with depth, though modern techniques can manipulate beam delivery to optimize dose distribution.

Proton therapy represents an advanced form of radiation treatment that uses protons instead of X-rays. The unique physical properties of protons allow them to deposit most of their energy at a specific depth (the Bragg peak) with minimal exit dose beyond the tumor. This characteristic makes proton therapy particularly valuable for treating tumors near critical structures like the brain, spinal cord, and eyes, as well as for pediatric cancers where minimizing radiation to healthy tissues is especially important.

What Are the Different Types of Radiation Therapy?

The main types of radiation therapy are external beam radiation therapy (EBRT), where radiation is delivered from a machine outside the body, and internal radiation therapy (brachytherapy), where radioactive sources are placed inside or near the tumor. Each type has specific advantages depending on the cancer type and location.

Understanding the different types of radiation therapy helps patients know what to expect from their treatment. The choice of radiation type depends on the cancer's location, size, and stage, as well as the patient's overall health and treatment goals. Many patients receive a combination of different radiation approaches as part of their comprehensive cancer treatment plan.

External Beam Radiation Therapy (EBRT)

External beam radiation therapy is the most common form of radiation treatment, used in approximately 80% of patients who receive radiotherapy. During EBRT, a large machine called a linear accelerator (LINAC) directs high-energy radiation beams at the tumor from outside the body. The machine can rotate around the patient to deliver radiation from multiple angles, allowing the beams to converge on the tumor while spreading the dose across healthy tissues.

Before treatment begins, patients undergo a detailed planning process called simulation. During simulation, imaging scans (usually CT, sometimes combined with MRI or PET) are performed with the patient in the exact position they'll be in during treatment. These images help the medical team map the tumor's location precisely and identify nearby healthy structures that need protection. Small tattoo dots or skin marks may be placed to ensure accurate positioning at each treatment session.

The actual treatment sessions are brief. Patients lie on a treatment table while the machine positions itself around them. The radiation delivery typically takes only 2-5 minutes, though the entire appointment may last 10-20 minutes due to positioning and verification procedures. Treatments are usually given once daily, five days per week, for 2-7 weeks, depending on the cancer type and treatment goals.

Internal Radiation Therapy (Brachytherapy)

Brachytherapy, also called internal radiation therapy, involves placing radioactive sources directly inside or very close to the tumor. The term "brachytherapy" comes from the Greek word "brachy," meaning short distance, reflecting how the radiation travels only a short distance from the source. This approach allows delivery of high radiation doses to the tumor while dramatically reducing exposure to surrounding healthy tissues.

There are two main types of brachytherapy based on the dose rate and duration of treatment. High-dose-rate (HDR) brachytherapy uses powerful radioactive sources that are temporarily placed in the body for a few minutes at a time, often through thin tubes or catheters inserted into the tumor region. Low-dose-rate (LDR) brachytherapy involves permanently implanting small radioactive seeds directly into the tumor, where they release radiation slowly over weeks to months until they become inactive.

Brachytherapy is commonly used to treat prostate cancer, cervical cancer, breast cancer, and certain head and neck cancers. The procedure may require anesthesia – either local, regional, or general – depending on the treatment site and technique used. Temporary implants may be placed during a brief outpatient procedure or may require a short hospital stay.

Systemic Radiation Therapy

Some radiation treatments are delivered as radioactive medicines that travel through the bloodstream to reach cancer cells throughout the body. These systemic radiation therapies include radioactive iodine for thyroid cancer, radium-223 for bone metastases from prostate cancer, and various radioimmunotherapy agents that combine radioactive particles with antibodies targeting specific cancer cells.

When receiving systemic radiation therapy, patients may need to follow special precautions for a period after treatment to minimize radiation exposure to family members and others. The duration and extent of these precautions depend on the specific radioactive material used and the dose administered.

How Do I Prepare for Radiation Therapy?

Preparation for radiation therapy includes a consultation with your radiation oncologist, imaging scans (CT simulation) to map the treatment area, creation of custom positioning devices if needed, and detailed treatment planning. The preparation process typically takes 1-2 weeks before your first treatment session.

Proper preparation for radiation therapy is essential for ensuring accurate treatment delivery and optimal outcomes. The preparation process involves several steps designed to precisely identify the treatment area, create a personalized treatment plan, and ensure you can maintain the exact same position during each treatment session.

Initial Consultation

Your first appointment with a radiation oncologist involves a comprehensive review of your medical history, previous treatments, and diagnostic imaging studies. The radiation oncologist will explain the recommended treatment approach, expected outcomes, and potential side effects specific to your situation. This is an excellent opportunity to ask questions about the treatment process, what to expect during and after therapy, and how to manage potential side effects.

During the consultation, the medical team will also assess factors that might affect your treatment, such as your ability to lie still for the required time, any implanted medical devices, or previous radiation treatments to the same area. If you have concerns about being in enclosed spaces or lying still, discuss these with your care team so they can accommodate your needs.

CT Simulation and Planning

The simulation appointment is a crucial step where detailed imaging creates a roadmap for your treatment. You'll lie on a CT scanner table in the same position you'll be in during actual treatment sessions. If you're receiving treatment to the head or neck area, a custom plastic mesh mask may be molded to fit your face and head, helping ensure precise positioning. For other body areas, cushions, molds, or other positioning devices may be created.

During simulation, you may receive small permanent tattoo marks (tiny dots about the size of a freckle) or temporary skin markings. These serve as reference points to help technologists position you accurately at each treatment session. The entire simulation appointment typically takes 1-2 hours.

After simulation, a team of specialists including your radiation oncologist, medical physicists, and dosimetrists work together to create your treatment plan. Using sophisticated computer software, they determine the optimal beam angles, radiation doses, and delivery techniques to maximize tumor treatment while protecting healthy tissues. This planning process may take several days to complete.

What to Do Before Starting Treatment

Once your treatment plan is finalized, you'll receive instructions about preparing for your treatment sessions. General recommendations include:

• Stop smoking if you smoke: Smoking reduces blood oxygen levels, making radiation less effective and increasing side effects. Your healthcare team can provide resources to help you quit.
• Protect skin markings: If you have temporary skin markings, avoid washing them off. You can shower but avoid scrubbing the marked areas with soap.
• Arrange transportation: While you can usually drive yourself to appointments, having someone available for transportation is helpful, especially later in treatment when fatigue may develop.
• Prepare for daily commitments: Radiation therapy requires daily visits for several weeks. Plan accordingly with work, childcare, or other responsibilities.

What Happens During Radiation Therapy Treatment?

During each radiation therapy session, you'll lie on a treatment table while technologists position you precisely using your skin marks and immobilization devices. The actual radiation delivery takes 2-5 minutes and is completely painless – you won't see, feel, or hear the radiation. The entire appointment typically takes 10-20 minutes.

Understanding what to expect during your treatment sessions can help reduce anxiety and make the experience more manageable. While the specifics may vary depending on the type of radiation and treatment area, the general process is similar for most external beam treatments.

Arriving for Your Appointment

When you arrive at the radiation oncology department, you'll typically check in and wait briefly before being called to the treatment room. Wear comfortable, loose-fitting clothing that's easy to remove from the area being treated. Avoid applying lotions, powders, perfumes, or deodorants to the treatment area, as these can interfere with radiation delivery and irritate the skin.

You'll be asked to remove clothing from the treatment area and may be given a hospital gown. The treatment room contains the linear accelerator – a large machine that can rotate around the treatment table. While the machine may appear intimidating at first, it doesn't touch you during treatment.

Positioning and Verification

Radiation therapists (technologists) will help you onto the treatment table and position you using your skin marks and any immobilization devices created during simulation. They may take X-ray or CT images to verify your position matches the treatment plan – a process called image guidance. This verification ensures the radiation targets exactly the planned area.

Once you're properly positioned, the therapists will leave the treatment room and operate the machine from an adjacent control room. Although you'll be alone during the actual radiation delivery, the therapists can see you on video monitors and hear you through an intercom. If you need assistance or feel uncomfortable at any point, you can speak to them immediately, and they can stop the treatment.

Radiation Delivery

During treatment, the linear accelerator may move around you, delivering radiation from different angles. You'll hear clicking and humming sounds from the machine – this is normal and indicates the machine is working. The radiation itself is invisible and painless – you won't feel anything while the beam is on.

It's crucial to remain completely still during treatment to ensure the radiation hits the intended target. You can breathe normally, but avoid large movements. For some treatments (particularly lung or liver cancers), you may be asked to hold your breath briefly during radiation delivery to account for organ movement with breathing.

Children who have difficulty remaining still may receive light sedation or general anesthesia for their treatments. A parent or caregiver can usually stay with the child until they fall asleep and be present when they wake up.

What Are the Side Effects of Radiation Therapy?

Common side effects of radiation therapy include fatigue, skin changes (redness, dryness, peeling) in the treated area, and site-specific effects depending on the treatment location. Most side effects develop gradually during treatment, peak 1-2 weeks after completion, and resolve within weeks to months. Some late effects may develop months or years later.

Side effects from radiation therapy occur because the treatment affects healthy cells in the treatment area along with cancer cells. Unlike cancer cells, healthy cells can repair themselves, which is why most side effects are temporary. The type and severity of side effects depend on the treatment area, radiation dose, treatment technique, and individual factors such as overall health and other treatments being received.

Early (Acute) Side Effects

Early side effects typically begin within the first few weeks of treatment and may continue for several weeks after treatment ends before improving. The most common early side effects include:

Fatigue is the most frequently reported side effect of radiation therapy, affecting most patients to some degree. Radiation-induced fatigue develops gradually during treatment and may persist for weeks to months after treatment completion. The fatigue differs from normal tiredness – it's often described as a deep exhaustion that isn't fully relieved by sleep. While the exact cause isn't fully understood, it likely relates to the body's energy expenditure in repairing radiation damage and fighting cancer.

Managing fatigue involves balancing rest with activity. While it may seem counterintuitive, regular gentle exercise has been shown to reduce cancer-related fatigue. Taking short rest periods throughout the day rather than one long nap can help maintain energy levels. Fatigue typically improves gradually over weeks to months after treatment ends.

Skin changes in the treatment area are common and progress through predictable stages. Initially, the skin may become slightly pink, similar to a mild sunburn. As treatment continues, the skin may become darker, dry, itchy, and may peel. In more severe cases, the skin may become moist and tender, particularly in areas where skin folds rub together (such as the armpit or under the breast).

To minimize skin reactions, keep the treated area clean and dry, avoid tight clothing that rubs the area, protect the skin from sun exposure, use mild unscented soap, and apply recommended moisturizers. Avoid using heating pads, ice packs, or products containing alcohol or perfumes on the treated area. Your healthcare team will provide specific skin care instructions.

Site-Specific Side Effects

In addition to general side effects, radiation therapy causes effects specific to the body part being treated:

Head and neck radiation may cause mouth sores (mucositis), dry mouth (xerostomia), difficulty swallowing, taste changes, and throat soreness. Hair loss occurs only in the treatment area – for example, scalp hair may be affected by brain radiation, while facial hair may be affected by treatment to the face or neck. Dental problems can develop because radiation affects saliva production and may make teeth more susceptible to decay.

Chest radiation (for lung, breast, or esophageal cancers) may cause difficulty swallowing, heartburn-like symptoms, or shortness of breath. Breast radiation may cause breast swelling, tenderness, and skin changes.

Abdominal or pelvic radiation may cause nausea, diarrhea, bladder irritation (increased frequency and urgency of urination), and for treatments near reproductive organs, potential effects on fertility. Women may experience vaginal dryness and, if the ovaries are in the treatment field, possible early menopause. Men may experience erectile dysfunction, particularly after prostate radiation.

Late (Chronic) Side Effects

Late side effects may develop months to years after radiation therapy ends. While less common than early effects with modern treatment techniques, they can sometimes be permanent. Late effects may include:

• Fibrosis: Scar tissue formation that can cause the treated area to feel firm or tight
• Lymphedema: Swelling due to lymphatic system damage, particularly after radiation to areas with lymph nodes
• Secondary cancers: A small increased risk of developing a new cancer in the treated area, typically appearing decades later
• Organ-specific effects: Such as dry mouth, bladder problems, or bowel changes that persist long-term

For children receiving radiation therapy, additional considerations include potential effects on growth and development. Lower radiation doses are typically used for children, and treatment plans are carefully designed to minimize exposure to developing tissues. Long-term follow-up is essential to monitor for late effects.

Is Radiation Therapy Safe for People Around Me?

With external beam radiation therapy, no radiation remains in your body after each treatment session – you are NOT radioactive and can safely be around family, friends, children, and pregnant women without restrictions. Internal radiation (brachytherapy) or radioactive medicines may require temporary precautions.

One of the most common concerns patients have about radiation therapy relates to safety for family members and others. Understanding what happens to radiation in your body helps address these concerns.

External Beam Radiation

When receiving external beam radiation therapy, the radiation beams pass through your body and are absorbed or exit on the other side – they do not stay in your body. Think of it like a flashlight beam passing through a window: when the light is turned off, no light remains in the window. Similarly, once the radiation machine turns off, no radiation remains in your body.

This means you can immediately and safely:

• Hug and kiss family members, including children
• Sleep in the same bed as your partner
• Be around pregnant women
• Hold infants and small children
• Use shared bathrooms and kitchens
• Resume normal daily activities

Internal Radiation and Radioactive Medicines

If you receive brachytherapy or radioactive medicines, the situation is different because radioactive material is placed inside your body. The precautions needed depend on the type and amount of radioactive material used:

Permanent seed implants (such as those used for prostate cancer) emit low levels of radiation for weeks to months. While you can usually resume normal activities shortly after the procedure, you may be advised to limit close contact with pregnant women and small children for a period, typically avoiding having them sit on your lap for extended periods.

Temporary implants are removed before you leave the hospital, after which no radiation remains in your body and no precautions are needed.

Radioactive medicines are eliminated from your body through urine, stool, sweat, and saliva over time. Precautions may include using a separate bathroom, flushing twice after using the toilet, sleeping in a separate bed, and maintaining distance from others for a specified period. Your healthcare team will provide detailed written instructions about any necessary precautions and how long they should be followed.

How Effective Is Radiation Therapy for Cancer?

Radiation therapy can cure many cancers, particularly when detected early. It contributes to cure in approximately 40% of all cancer patients. Radiation is the primary treatment for some cancers and combines with surgery or chemotherapy for others. Effectiveness varies by cancer type, stage, and treatment approach.

Radiation therapy plays a critical role in cancer treatment, either as a primary treatment modality or in combination with surgery, chemotherapy, immunotherapy, or targeted therapy. Understanding how radiation fits into cancer treatment helps patients appreciate its value and set appropriate expectations.

Curative Radiation Therapy

For many cancers, radiation therapy is delivered with curative intent – the goal is to eliminate the cancer entirely. Radiation can cure various cancers as a sole treatment or as part of multimodal therapy. Examples include:

• Early-stage prostate cancer: Both external beam radiation and brachytherapy provide cure rates comparable to surgery
• Early-stage lung cancer: Stereotactic radiation can cure small lung tumors in patients who cannot undergo surgery
• Head and neck cancers: Combined radiation and chemotherapy cures many patients while preserving speech and swallowing function
• Cervical cancer: Radiation with chemotherapy is curative for many stages
• Skin cancers: Radiation provides excellent cure rates with good cosmetic outcomes

Adjuvant Radiation Therapy

Adjuvant radiation is given after the primary treatment (usually surgery) to destroy any remaining cancer cells that cannot be seen but may be present. This approach reduces the risk of cancer recurrence. Common examples include radiation after breast-conserving surgery (lumpectomy) for breast cancer and radiation after surgery for brain tumors or high-risk rectal cancer.

Palliative Radiation Therapy

When cure is not possible, radiation therapy can effectively relieve symptoms and improve quality of life. Palliative radiation can shrink tumors causing pain, bleeding, or obstruction. It's particularly effective for bone metastases (cancer spread to bones), where it can rapidly relieve pain and prevent fractures, and for brain metastases, where it can reduce neurological symptoms.

Palliative radiation courses are typically shorter than curative treatments, often consisting of only a few treatments or even a single treatment session.

What Are Special Considerations for Children Receiving Radiation?

Children may receive radiation therapy for various cancers, but special considerations apply because developing tissues are more sensitive to radiation. Lower doses are used when possible, and alternative treatments may be preferred. Long-term follow-up is essential to monitor for late effects on growth, development, and organ function.

While cancer in children is relatively rare, radiation therapy remains an important treatment option for pediatric malignancies. The approach to treating children differs from adults due to their developing bodies and longer life expectancy, which increases the importance of minimizing long-term side effects.

Children's bodies are more sensitive to radiation than adults' because their cells are dividing more rapidly during growth and development. This sensitivity means that while radiation may be effective against tumors, there's also greater potential for effects on normal developing tissues. For this reason, radiation oncologists carefully weigh the benefits and risks when considering radiation for pediatric patients.

When radiation is necessary, several strategies help minimize long-term effects. Radiation doses are typically lower than those used for adults. Treatment plans are meticulously designed to avoid critical developing structures whenever possible. Proton therapy, when available, may be preferred because it reduces radiation exposure to tissues beyond the tumor.

Potential late effects in children include effects on bone and muscle growth (which may cause asymmetries or shortened stature), hormone problems if the pituitary gland is affected, learning and cognitive effects from brain radiation, secondary cancers, and effects on fertility. Children who receive radiation therapy require long-term follow-up, often continuing into adulthood, to monitor for these late effects and intervene early if they develop.

How Does Radiation Therapy Affect Fertility and Pregnancy?

Radiation therapy can affect fertility if treatment is given to reproductive organs (ovaries, testes) or the pituitary gland. Effects range from temporary to permanent depending on the radiation dose and treatment area. Fertility preservation options should be discussed before treatment. Radiation therapy during pregnancy is generally avoided but can sometimes be given safely.

Fertility considerations are important for patients of reproductive age who require radiation therapy. The effects on fertility depend primarily on whether reproductive organs are in or near the treatment field and the radiation dose they receive.

Effects on Female Fertility

For women, radiation to the pelvis can damage the ovaries, potentially causing temporary or permanent infertility and early menopause. The ovaries are sensitive to radiation, and even moderate doses can significantly reduce the egg supply. Women of childbearing age should discuss fertility preservation options before starting treatment, which may include egg or embryo freezing, or in some cases, surgical repositioning of the ovaries away from the radiation field (oophoropexy).

Radiation to the uterus can affect its ability to support a pregnancy, potentially increasing risks of miscarriage, preterm birth, or low birth weight in future pregnancies. Women who have received pelvic radiation and become pregnant should be monitored as high-risk pregnancies.

Effects on Male Fertility

For men, radiation to the pelvis or testes can affect sperm production and testosterone levels. The testes are highly sensitive to radiation – even scattered radiation from treatment of nearby structures can affect fertility. Sperm banking before treatment is an option for men who wish to preserve fertility. Testicular shielding may be used when possible to reduce radiation exposure to the testes.

Unlike eggs, sperm are continuously produced throughout a man's life, so some recovery of sperm production may occur after radiation, depending on the dose received. However, this recovery is not guaranteed, and some men experience permanent infertility.

Radiation During Pregnancy

Radiation therapy during pregnancy is generally avoided due to potential risks to the developing fetus, which include miscarriage, birth defects, growth problems, and childhood cancer. In most cases, treatment can be delayed until after delivery or alternative therapies can be used during pregnancy.

However, in urgent situations where delaying treatment would significantly harm the mother, radiation may be carefully administered, especially if the treatment area is far from the uterus (such as for head and neck cancers) and proper shielding can protect the fetus. These situations require careful planning by a specialized team.

If you are pregnant or think you might be pregnant, inform your healthcare team before starting any radiation therapy planning.