TBI - Total Body Irradiation is a technique which involves treating the entire body with radiation therapy (RT).
The aim is to
- Kill residual malignant cells
- Deplete the bone marrow to allow space for engraftment
The addition of RT to chemotherapy has some advantages:
- No sparing of “sanctuary sites” - CNS and testes
- Dose delivered is relatively homogeneous and independent of blood supply.
- No cross resistance with other agents
- If there is any compromise of liver/ kidney, the dose distribution is still maintained
- Dose distribution can be tailored to block sensitive areas.
This technique originally used large single fractions - but this caused significant damage to normal tissues. Now treatment is fractionated (split up into small fractions or amounts of radiotherapy). Treatment is still effective, but far less toxic.