Fractionated total body irradiation: some radiobiological considerations.

Fractionated total body irradiation (TBI), as conditioning regimen for bone marrow transplantation in the treatment of non-lymphocytic leukaemia, has proved to be less toxic than single fraction TBI. However, higher relapse rates are reported. The linear quadratic (LQ) model has been applied to calculate equivalent total therapeutic doses as well as equivalent tolerance doses for fractionated TBI. The LQ model predicted that escalating total doses for fractionated TBI will still result in acceptable toxicity to lung while achieving better disease control. There is published clinical data supporting our conclusion from this radiobiological analysis.