Abstract: In cases where material properties of a structure within or outside a patient receiving radiotherapy treatment, robust planning can be used, based on different scenarios with different material property values using a material override function present in the treatment planning system. A computer-based method of generating a radiotherapy treatment plan for a patient, based on an image of the patient and a desired dose. In cases where material properties of a structure within or outside a patient receiving radiotherapy treatment, robust planning can be used, based on different scenarios with different material property values using a material override function present in the treatment planning system. Robust planning is performed based on the at least two scenarios to provide robust evaluation data for each of the at least two scenarios and/or a robust optimized treatment plan with respect to all values in the set of material override values.