Physics Bucharest 2017

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