Since radiation dose escalation to a large volume of tumour inevitably will induce higher toxicity than is currently the case, efforts must be made to limit the volume of tissue irradiated. Moreover, the irradiation of larger tumour volumes leads to a lower achievable tumour dose when keeping the normal tissue doses constant. Central is thus the question whether it would be possible to limit the volume of tumour to be boosted by selectively escalating the radiation dose to specific disease sites which are theoretically more prone to relapse.