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Therapeutic ratio
• TR describes the probability of tumour
control (TCP) versus normal tissue
complication (NTCP). Aim to cure with
minimal late side-effects
• Higher doses increase TCP but also
NTCP: usually accept a 5% risk of severe
late normal tissue toxicity except for spinal
cord (<1%)
• Clinical ways of
therapeutic ratio
•
Fractionation
•
Concurrent chemotherapy/biological
agents
•
reducing volume of normal tissue
irradiated or dose delivered e.g.
Conformal, Stereotactic XRT or
brachytherapy