Lower GI 2017

Therapeutic ratio (I)

) 1( NTCP TCP P − ⋅ = +

Easy to interpret: if TCP and NTCP are statistically independent, this is the probability of being cured without a complication

Has been used in several published studies

The same relative change in NTCP will have a much larger

influence on P +

for large NTCP relative to small NTCP

Face validity for non-fatal complications? A: TCP=40% and NTCP=40% ⇒ R=24% B: TCP=60% and NTCP=60% ⇒ R=24% …but proportion of patients with tumor control AND side-effects is 16% with treatment A versus 36% with treatment B