A database stores pre-calculated solutions each of which defines a radiation therapy treatment plan for a treatment volume associated with at least one target and at least one organ-at-risk. The pre-calculated solutions are divided into at least two groups each of which includes at least one pre-calculated solution. The pre-calculated solutions in a given group represent radiation therapy treatment plans which share a common beam configuration. A radiation therapy treatment plan (sc) is established based on the pre-calculated solutions as follows. A first user interface receives operator commands specifying criteria for selecting radiation therapy treatment plans from the database, the criteria defining a set of parameters for the treatment volume. In particular, the operator commands jointly specify criteria for selecting radiation therapy treatment plans from more than one of the at least two groups. When establishing a solution, a preference function is applied on at least two pre-calculated solutions to establish one and only one solution as a radiation therapy treatment plan (sc) meeting the criteria.
