Radiation oncologists involved in palliative treatment scenarios frequently prescribe repeated courses of radiotherapy to anatomically distinct parts of the body, e.g., because of newly arising painful bone metastases. Due to non-overlapping dose distributions and moderate biologically equivalent doses, this type of retreatment is not particularly challenging. The complexity of decision-making and treatment planning increases when the new lesion is located close to the previous target volume, even in the absence of direct re-irradiation of an already treated lesion.