TOTAL BODY IRRADIATION (TBI):
TRANSPLANT CONDITIONING
A complete guide to TBI โ how whole-body radiation prepares patients for bone marrow and stem cell transplants by destroying diseased marrow, eliminating residual malignant cells, and creating space for donor engraftment. Includes TBI for ALL, AML, lymphoma, and the transplant process in China.
analyticsAt a Glance
- check_circleTBI treats the entire body โ not a single tumour โ as part of conditioning before a stem cell or bone marrow transplant.
- check_circleDestroys the patient's diseased bone marrow, eliminates chemotherapy-resistant residual cancer cells, and suppresses the immune system to prevent rejection of donor cells.
- check_circleMost commonly used for acute leukaemia (ALL and AML), lymphoma, and myeloma requiring high-intensity conditioning.
- check_circleChina's transplant infrastructure offers haploidentical and matched transplants with TBI conditioning at USD 50,000-80,000 โ vs USD 250,000-450,000 in the US.
What Is Total Body Irradiation?
Total body irradiation (TBI) is a form of radiation therapy that treats the entire body rather than a single tumour. It is almost exclusively used as part of the conditioning regimen before a haematopoietic stem cell transplant (HSCT) โ the preparation in the days before donor cells are infused.
โTBI prepares the ground. The donor stem cells are the seeds. Engraftment is the new immune system growing. Without effective conditioning, donor cells may be rejected and the disease is more likely to return.โ
Why TBI Is Used in Transplant Conditioning
TBI serves three roles simultaneously: myeloablation (destroying the patient's diseased bone marrow to create space for donor cells), immunosuppression (preventing the patient's immune system from rejecting the new cells), and anti-tumour effect (eliminating residual malignant cells that survived chemotherapy, including those in sanctuary sites like the CNS and testes).
Myeloablative vs Reduced-Intensity Conditioning
Myeloablative conditioning (MAC) uses high-dose TBI (12 Gy total) with cyclophosphamide to completely destroy the bone marrow. Reduced-intensity conditioning (RIC) uses lower TBI doses (2-4 Gy) combined with fludarabine, relying more on donor immune effect. MAC is preferred for young patients with high-risk disease; RIC is used for older patients or those with comorbidities.
Fractionated TBI โ Reducing Toxicity
Standard myeloablative TBI delivers 12 Gy in 6 fractions (2 Gy twice daily for 3 days), combined with cyclophosphamide chemotherapy. Fractionation compared to single-dose TBI significantly reduces pulmonary toxicity, cataracts, and late effects while maintaining anti-tumour efficacy.
Total Marrow Irradiation (TMI) โ A Modern Alternative
TMI delivers targeted radiation selectively to bone marrow sites (skeleton) while sparing lungs, kidneys, and liver using IMRT/tomotherapy. This may reduce late pulmonary and renal toxicity compared to conventional TBI while maintaining anti-leukaemic efficacy. Being evaluated in clinical trials at Chinese and Western centres.
Which Conditions Use TBI-Based Conditioning?
TBI-containing conditioning regimens are used primarily for haematological malignancies requiring allogeneic transplant, particularly where chemotherapy-only conditioning is less effective.
Acute Lymphoblastic Leukaemia (ALL) โ The Primary Indication
TBI-cyclophosphamide conditioning remains the standard for allogeneic HSCT in ALL, particularly for adult patients and children with high-risk features. TBI provides superior CNS and testicular penetration compared to chemotherapy alone โ important because ALL can relapse in these sanctuary sites that chemotherapy does not reliably reach.
Acute Myeloid Leukaemia (AML) and Myeloid Diseases
TBI-based conditioning is used for AML, myelodysplastic syndrome (MDS), and myeloproliferative neoplasms requiring allogeneic HSCT. Whether TBI-based or chemotherapy-only conditioning is superior for AML remains debated โ centre practice and patient age and fitness guide the choice.
Lymphoma and Multiple Myeloma
Selected patients with relapsed or refractory lymphoma (particularly T-cell lymphomas and Hodgkin lymphoma relapsing after autologous transplant) may receive TBI as part of reduced-intensity allogeneic conditioning. Multiple myeloma conditioning for autologous HSCT uses melphalan without TBI as standard; TBI is reserved for specific allogeneic protocols.
Non-Malignant Haematological Conditions
TBI-based conditioning is used for selected patients with aplastic anaemia, thalassaemia, sickle cell disease, and primary immunodeficiencies requiring allogeneic HSCT when chemotherapy-only conditioning is inadequate. The balance between conditioning intensity and late effects is carefully individualised.
The TBI Treatment Process
TBI is delivered over several days as part of a sequential conditioning regimen immediately before stem cell transplant.
- 1
Pre-Transplant Assessment and Conditioning Planning
Transplant physician and radiation oncologist jointly plan the conditioning regimen โ TBI dose, fractionation, and sequencing with chemotherapy. Lung function, renal function, and prior radiation history reviewed.
- 2
TBI Simulation and Lung Block Fabrication
Planning CT and patient positioning established. Custom lung blocks (or IMRT plans for TMI) fabricated to reduce pulmonary dose below the threshold for radiation pneumonitis.
- 3
Chemotherapy Conditioning (Before TBI)
Cyclophosphamide or other agents given before TBI in the conditioning sequence. The chemotherapy-TBI schedule runs over 3-6 days total.
- 4
Fractionated TBI Delivery
12 Gy delivered in 6 fractions (2 Gy twice daily, 6 hours apart) over 3 days. Extended distance from linac to patient ensures uniform dose across the whole body. Lung blocks reduce lung dose to tolerable levels.
- 5
Stem Cell Infusion and Engraftment
Donor stem cells infused 24-48 hours after the last TBI fraction. Engraftment โ the new cells populating the bone marrow โ typically occurs at 2-4 weeks. Intensive supportive care during this period.
Key Numbers
- 12 GyStandard Myeloablative TBI DoseDelivered in 6 fractions of 2 Gy twice daily over 3 days. Single-dose TBI (7.5-8 Gy) used at some centres.
- 2-4 GyReduced-Intensity TBI Dose (RIC)Combined with fludarabine for older patients or those with significant comorbidities.
- 2-4 wksTime to EngraftmentAfter TBI and stem cell infusion, the new immune system typically begins producing blood cells within 2-4 weeks.
- USD 50-80KAllogeneic HSCT Including TBI in Chinavs USD 250,000-450,000 in the US. CancerFax coordinates transplant and TBI access in China.
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Frequently Asked Questions
About TBI
What are the main side effects of TBI?
Immediate side effects include nausea, fatigue, skin redness, parotid swelling, and mucositis. The most important late effects are pulmonary toxicity (radiation pneumonitis and pulmonary fibrosis โ substantially reduced by lung shielding), cataracts (nearly universal at high dose; surgically correctable), hypothyroidism, growth impairment in children, and secondary malignancy risk. Modern fractionated TBI with lung shielding has significantly reduced serious late toxicity compared to historical single-fraction approaches.
Is TBI available in China for transplant patients?
Yes. China has substantial transplant infrastructure, including at Peking University People's Hospital (the centre that developed the Beijing Protocol for haploidentical transplant), and multiple other academic transplant centres. TBI-based conditioning is available at these centres as part of full allogeneic HSCT programmes. The total cost of allogeneic transplant including TBI conditioning in China is approximately USD 50,000-80,000 โ compared to USD 250,000-450,000 in the US. CancerFax coordinates transplant access for international patients.
Can TBI be avoided in some transplant protocols?
Yes. For AML and several other indications, chemotherapy-only conditioning (typically busulfan-cyclophosphamide or fludarabine-busulfan) achieves comparable outcomes without radiation. The decision between TBI-based and chemotherapy-only conditioning depends on the disease, patient age, prior radiation history, and centre expertise. For ALL, TBI-based conditioning is generally preferred due to its superior CNS penetration. A specialist transplant haematologist's recommendation based on the full clinical picture is essential.
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This content is for informational purposes only and does not constitute medical advice. All treatment decisions must be made in consultation with a qualified transplant haematologist and radiation oncologist.