The invention relates to the planning of a radiation therapy treatment of at least one structure in a region of a patient body. A planning unit obtains a first treatment plan generated on the basis of a planning image of the body region and on the basis of dose objectives. Moreover, the planning unit receives a further image of the body region of the patient body, determines a transformation for generating an adapted treatment plan from the first treatment plan and/or for generating an adapted dose distribution from the dose distribution corresponding to the first treatment plan on the basis of the further image and determines an adapted treatment plan on the basis of the transformation and/or the adapted dose distribution. In accordance with the invention, the transformation on the basis of the dose objectives