The ratio of relative risk (RRR), defined as the ratio of ERR for protons (ERRproton) to that for intensity-modulated photon therapy (ERRIMRT), of the medium patient for various dose-response models. Error bars represent the uncertainty in RRR due to variations in stray radiation exposures from proton therapy and IMRT in a population of ten prostate cancer patients. The response models were LNT, linear no-threshold; LEXP(10), linear-exponential rolling off at 10 Sv; LPLAT(10), linear-plateau rolling off at 10 Sv; LEXP(40), linear-exponential rolling off at 40 Sv; and LPLAT(40), linear-plateau rolling off at 40 Sv.