A radiation therapy planning system (10) includes an isodose line unit (36), a region of interest unit (52), and an optimization unit (58). The isodose line unit (36) receives isodose lines planned for a volume of a subject. The region of interest unit (52) defines at least one isodose region of interest based on the received isodose lines. The optimization unit (58) generates an optimized radiation therapy plan based on the at least one defined isodose region of interest and at least one dose objective for the defined region of interest.
