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Total body irradiation as part of conditioning | CION Cancer Clinics
Total body irradiation, or TBI, is radiotherapy to the whole body given with chemotherapy before some stem cell transplants. It is usually spread over a few days, often twice a day. You feel nothing during the beam and are not radioactive afterwards. Sickness, tiredness and jaw swelling can follow within hours, and some effects appear years later. This page explains each session and what to ask. At CION Cancer Clinics, our haematology team assesses whether a transplant or CAR-T fits your situation and coordinates care with qualified centres.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What is total body irradiation, and what will it feel like?
- What happens before and during each session?
- What should you know before the first session?
- What side effects should you expect, and when?
- What do families worry about that is not true?
- Which words will you hear from the radiation team?
- Who is TBI not suitable for, and what can this page not tell you?
- Common questions about total body irradiation
The short answer
What is total body irradiation, and what will it feel like?
Total body irradiation, often written TBI, is radiotherapy given to the whole body as part of conditioning before a stem cell transplant. You lie still while the machine treats you; you feel nothing during the beam, and the side effects come in the hours and days afterwards.
Why radiation is added to chemotherapy
Radiation reaches places some chemotherapy drugs reach poorly, such as the brain, spinal fluid and testes. It also lowers the immune system strongly, which helps donor cells take hold. That is why it is used in some plans for leukaemia, especially acute lymphoblastic leukaemia.
How it is usually given
Most centres give TBI over a few days, often split into two sessions a day with a gap between them. Some low-dose plans use a single short session. Splitting the dose lets healthy tissue recover between sessions. Your team will give you the exact schedule before admission.
Where it fits in the countdown
TBI sits inside the conditioning days, before or after the chemotherapy depending on the plan. You usually stay admitted on the transplant ward and travel to the radiation room for each session. A nurse or attendant goes with you, because the counts and your energy can drop quickly.
Not every transplant uses radiation. Many plans use chemotherapy alone, and the choice depends on the disease and your health.From planning to treatment
What happens before and during each session?
The planning visit
You meet the radiation oncologist and have a planning scan. The team measures your body and decides your position. Small skin marks may be made so you can be lined up the same way each time.
Shields for the lungs
The lungs are sensitive to radiation. Many centres place blocks or shields to lower the dose reaching them. Some also shield the kidneys or eyes, depending on the plan.
Lying still in the room
You lie or stand in a set position, often further from the machine than in normal radiotherapy, so the beam covers your whole body. Staff leave the room but watch and talk to you by camera and intercom.
After the session
You return to the transplant ward. Medicines to prevent sickness are usually given before each session. Tell the nurse about any sickness, headache or tummy upset so it can be treated quickly.
Not sure whether this applies to you?
Ask an oncologistPractical points
What should you know before the first session?
- Sessions can take longer than ordinary radiotherapy, so ask about music or talking to staff
- Wear loose cotton clothes with no metal, or the gown provided
- Avoid creams and powders on the skin unless the team approves them
- Children may need sedation to stay still; parents can usually stay until the beam starts
- You are not radioactive afterwards and can be with family safely
- Ask about sperm or egg storage before the first session
Side effects
What side effects should you expect, and when?
Some effects appear within hours. Others appear months or years later. Knowing the difference helps you plan follow-up.
Within hours or days
Feeling sick and vomiting, tiredness, loose motions, headache, and sometimes swelling and soreness of the salivary glands near the jaw. Mild fever can occur too.
Anti-sickness medicine works best when given before the sickness starts.In the following weeks
Together with chemotherapy, TBI brings the counts down and makes the mouth and gut lining sore. Hair falls out. The skin may darken or feel dry.
Tell the team about
- Fever or shivering
- A dry cough or breathlessness
Months and years later
Cataracts, an underactive thyroid, reduced fertility, slower growth in children, and a small rise in the chance of a second cancer later in life.
Long-term checks usually include
- Eye and thyroid tests
- Hormone and growth review
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Commonly believed
What do families worry about that is not true?
"After radiation he will give off rays, so the children must stay away."
TBI uses an external beam. Nothing stays in the body when the machine switches off. The reason to keep sick children away during a transplant is infection, not radiation.
"Radiation to the whole body will burn the skin badly."
The dose is spread across the body and split into sessions. Most people notice darker or dry skin, not burns. Tell the nurse if the skin becomes red, broken or painful, so it can be treated.
"If one session is missed, the whole plan fails."
The schedule is kept as close to plan as possible because timing matters. If you are unwell, the team decides what to do. Do not worry alone; tell them early rather than trying to push through.
"Our daughter will never be able to have children after TBI."
Fertility is very often affected, and families should be told plainly. But options such as storing eggs, sperm or tissue may exist before treatment. Ask early, because the window closes once conditioning begins.
On your plan
Which words will you hear from the radiation team?
- Fraction
- One session of radiation. A dose split into several fractions is gentler on healthy tissue.
- Gray (Gy)
- The unit used to measure a radiation dose. Your plan will state the total and the amount in each session.
- Lung shielding
- Blocks placed between the beam and the lungs to lower the dose they receive.
- Low-dose TBI
- A much smaller single dose used in some reduced intensity plans, mainly to lower the immune system.
- Cranial boost
- Extra radiation to the brain in some leukaemia plans, where cancer cells can hide.
Being straight with you
Who is TBI not suitable for, and what can this page not tell you?
TBI is usually avoided in people who have already had a lot of radiation, those with serious lung disease, and very young children, where the effects on growth and learning weigh more heavily. Many myeloma and lymphoma transplants do not use it at all.
What this page cannot tell you
It cannot tell you whether TBI is right for your disease, what dose you will receive, or how you will feel. Those depend on the transplant plan, your earlier treatment and your health. Only the transplant and radiation teams can explain your own schedule.
What to ask before you agree
Why is radiation part of my plan? Is there a chemotherapy-only option, and what would it change? Which organs will be shielded? What long-term checks will I need, and who will arrange them? Ask for written answers you can take home.
CION's haematology team reviews the case, presents it at a tumour board and coordinates referral with qualified transplant centres. We can help you prepare these questions.Questions we are asked
Common questions about total body irradiation
Does total body irradiation hurt?
The beam itself cannot be felt. What some people find hard is lying in one position for a long time. Tell the staff if you are uncomfortable before the session starts, so they can adjust pillows or supports. Feeling sick or a headache afterwards is common and can be treated.
How many days does TBI take?
Most plans spread it over a few days, often with two sessions a day. Low-dose plans may use a single session. It is usually given in the days just before the transplant, alongside chemotherapy. Your team will give you the exact dates before admission.
Will I be radioactive after TBI?
No. TBI comes from a machine outside the body, and nothing remains once it switches off. You can be with family and children safely. The precautions you will see on the transplant ward are about preventing infection, not radiation.
Why do my jaw and cheeks feel swollen after the first session?
The salivary glands near the jaw are sensitive to radiation and can swell and ache within the first day. It usually settles on its own within a few days. Tell the nurse, who can give pain relief and check it is not something else.
Can a child have TBI?
Yes, some children with leukaemia receive it, but teams weigh it carefully because of later effects on growth, hormones and learning. Young children may need sedation to stay still. Parents should ask what long-term follow-up is planned and who will provide it.
Will TBI affect my eyes?
Cataracts, a clouding of the lens, are a known later effect and may appear years afterwards. They can usually be treated with routine eye surgery. Regular eye checks after transplant help catch them early. Tell your doctor if your vision becomes blurred or glare bothers you.
Can I eat before a TBI session?
Many centres suggest a light meal, and some ask you to avoid eating just before the session to reduce sickness. Follow your own centre's instructions. Tell the team if you cannot keep food down, so they can adjust the medicines.
Does CION give total body irradiation?
TBI is given at transplant centres as part of a transplant programme. CION's haematology team reviews your case, presents it at a tumour board and coordinates referral with qualified centres. We can help you understand the plan and prepare questions before admission.
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Sources
- Cancer Research UK — Bone marrow and stem cell transplants
- National Cancer Institute — Definition of total-body irradiation
- National Cancer Institute — Stem Cell Transplants in Cancer Treatment
- American Cancer Society — Stem Cell Transplant for Cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Conditioning Chemotherapy: What It Does and WhyThe chemotherapy given alongside TBIMyeloablative vs Reduced Intensity ConditioningWhy some plans use full-dose and others low-dose TBITransplant Day Zero: What Actually HappensWhat follows once conditioning endsRadiation therapy guideHow radiotherapy works in general
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Radiation in your transplant plan?
Share the plan with us. CION's haematology team will review it, discuss the case at a tumour board and help you prepare questions for the transplant centre.