Radiation Therapy

Radiation therapy is a cancer treatment that uses high-energy beams of radiation to damage or destroy cancer cells so they can no longer grow and divide.

The radiation works by breaking the DNA (the genetic material inside a cell) of cancer cells. When the DNA is damaged beyond repair, the cell stops dividing and eventually dies. The body then clears these dead cells over time. Because the beams can be aimed very precisely, doctors try to expose as little healthy surrounding tissue as possible. Treatment is usually delivered in many small sessions spread over several weeks, which gives healthy cells time to recover between sessions while keeping the pressure on cancer cells.

Radiation therapy is used across a wide range of cancers, either as the main treatment or alongside surgery and chemotherapy (drug-based cancer treatment). The goal can be to cure, to shrink a tumour before surgery, to destroy remaining cancer cells after surgery, or to relieve symptoms when a cure is not possible.

• Breast cancer — often given after surgery to lower the chance of the cancer returning
• Prostate cancer — used as a primary treatment or after surgery
• Lung cancer — given alone or with chemotherapy
• Head and neck cancers — including throat, mouth, and voice-box tumours
• Brain tumours — to slow growth or relieve pressure
• Cervical and uterine cancers — frequently combined with chemotherapy
• Rectal and colorectal cancer — often given before surgery to shrink the tumour
• Lymphoma (cancer of the lymph nodes, part of the immune system) — sometimes used after chemotherapy
• Bone metastases (cancer that has spread to bone) — to reduce pain and prevent fractures
• Skin cancers — including some non-melanoma types

Radiation therapy is not suitable for every patient or every cancer. Your oncologist (cancer specialist) will consider several factors before recommending it.

• Cancers that are already spread very widely throughout the body — systemic (whole-body) treatments such as chemotherapy are usually preferred
• Patients who have already received the maximum safe dose of radiation to the same area in a previous course of treatment
• Certain autoimmune conditions (diseases where the immune system attacks the body itself) that can make radiation side effects much worse
• Pregnancy — radiation is generally avoided, especially in the first three months, because of risk to the developing baby

Radiation therapy is a well-established treatment, but it does carry recognised side effects and risks, most of which depend on which part of the body is treated and what total dose is given.

• Fatigue (tiredness that does not go away with rest) — the most common side effect, builds up gradually over the course of treatment
• Skin irritation in the treated area — redness, dryness, peeling, or soreness, similar to a sunburn
• Hair loss in the treated area only — not necessarily all over the body
• Nausea and vomiting — more likely when the abdomen or brain is treated
• Mouth sores and difficulty swallowing — when the head or neck is treated
• Diarrhoea — when the abdomen or pelvis is treated
• Swelling (oedema) in the treated area
• Damage to nearby healthy tissues or organs — for example, lung inflammation when the chest is treated, or bladder irritation when the pelvis is treated
• Increased risk of infection if the bone marrow (the tissue inside bones that makes blood cells) is affected
• Long-term effects such as fibrosis (thickening and scarring of tissue) in the treated area, which can develop months or years later
• A very small risk of a secondary cancer developing in the treated area many years later

Preparing for radiation therapy involves several stages that happen before your very first treatment session. These steps are not about a single day — planning can take one to two weeks, though this varies between hospitals.

Before treatment begins, your team will usually ask you to: avoid significant changes to your weight, since the body position planned for your treatment needs to stay consistent; tell your doctor about all medications you take, including supplements, because some drugs can make radiation side effects worse; stop smoking if possible, as smoking reduces the effectiveness of radiation and slows healing; limit or avoid alcohol, especially if the treatment area is near the throat, mouth, or liver; and follow any fasting instructions given before a planning scan, usually no food for a few hours beforehand.

Tests and assessments that are usually done before starting radiation therapy include:

• Imaging scans — CT, MRI, or PET scans (a scan that shows where cancer cells are active) to map the exact location and size of the tumour
• Blood tests — to check overall health, kidney and liver function, and blood cell counts
• A simulation session — a dedicated planning appointment where you lie in the exact position you will be in during every treatment; the team makes body moulds or masks to keep you perfectly still
• Skin markings or small permanent tattoo dots — tiny reference marks placed on the skin to ensure the beam is aimed at exactly the same spot every session
• A treatment plan — a radiation oncologist and a medical physicist (a specialist who calculates precise radiation doses) work together to design a plan tailored to your tumour's shape and location

What happens during each treatment session, in order:

• 1. You change into a hospital gown and lie down on the treatment table in the position established during simulation.
• 2. Technicians (radiation therapists) position you carefully, using the skin markings as guides, and may use the body mould or mask to hold you still.
• 3. The team leaves the room. You will be alone, but they watch you continuously through a camera and can speak with you through an intercom.
• 4. The radiation machine — often a linear accelerator (a machine that generates and directs the radiation beam) — rotates around you, delivering the beam from several angles.
• 5. Each session is usually short. The actual delivery of radiation typically takes only a few minutes, though set-up time may make the total appointment longer.
• 6. You feel nothing during the beam delivery. The machine may make clicking or whirring sounds.
• 7. The technicians return, help you off the table, and you can leave. Most patients drive or travel home on their own.

After each session you can usually return home straight away, since radiation therapy itself does not require recovery in hospital. However, the cumulative effect of treatment builds up over weeks, so managing side effects and attending every scheduled session is an important part of care. Your oncology team will guide you throughout.

• Fatigue management: rest when needed, but light activity such as short walks is usually encouraged and can help maintain energy levels
• Skin care in the treated area: keep the skin clean and moisturised with gentle, unperfumed products as recommended by your team; avoid tight clothing over the area, hot water, and direct sun exposure
• Diet adjustments: if the throat, mouth, stomach, or pelvis is treated, your team may refer you to a dietitian (nutrition specialist); soft, easy-to-swallow foods or extra fluids may be needed
• Infection awareness: watch for signs such as fever, unusual redness, or swelling, and contact your team promptly if these appear
• Avoiding radiation exposure to others: external beam radiation (the most common type) does not make you radioactive — you are safe to be around family including children; if you receive internal radiation (brachytherapy, where a radioactive source is placed inside the body), your team will give specific guidance on temporary precautions
• Medication: your team may prescribe creams for skin reactions, medicines for nausea, or mouthwashes for mouth sores; always follow their specific instructions
• Follow-up appointments: imaging scans and blood tests are usually scheduled weeks to months after completing the full course, to assess how the tumour has responded; the exact schedule depends on your cancer type and the treatment given
• Long-term monitoring: regular check-ups continue for years after treatment, as some late side effects can appear months or years later
• Emotional support: feelings of anxiety, low mood, or exhaustion are common during and after treatment; many cancer centres offer counselling or support groups, and your team can refer you if needed