Radiobiological and Clinical Bases for Total Body Irradiation in the Leukemias and Lymphomas

Area of Science:

• Oncology
• Radiation Biology
• Hematology

Background:

• Therapeutic total body irradiation (TBI) is a key component in bone marrow transplantation conditioning regimens.
• While chemotherapy-only regimens exist, TBI remains vital for its antileukemic and immunosuppressive properties.
• The optimal TBI schedule, particularly regarding fractionation, is not definitively established.

Purpose of the Study:

• To review radiobiological and clinical data to assess the impact of TBI fractionation on leukemia cell killing, immunosuppression, and normal tissue toxicity.
• To explore how leukemia type influences sensitivity to TBI fractionation.
• To discuss potential adaptations of TBI schedules and future directions for individualization.

Main Methods:

• Review of existing radiobiological and clinical data on TBI fractionation.
• Analysis of leukemia cell sensitivity to fractionation based on leukemia type (AML, CML, ALL, NHL).
• Consideration of fractionation effects on immunosuppression and normal tissue toxicity.

Main Results:

• Leukemia cell sensitivity to TBI fractionation varies by type; AML cells show low sensitivity, while CML cells are sensitive. Data for ALL and NHL are inconclusive.
• The immunosuppressive effect of TBI is highly sensitive to fractionation.
• Normal tissues at risk also exhibit significant sensitivity to TBI fractionation and dose rate.

Conclusions:

• Fractionation of TBI can be cautiously adapted based on leukemia type, donor marrow status, and toxicity concerns.
• Further research is needed to determine the precise radiosensitivity of individual patient leukemias/lymphomas.
• Advancements in leukemia-cell culture techniques may enable personalized TBI schedules in the future.