1. A method for determining a radiation therapy dose distribution, comprising: selecting and downloading a treatment type for a patient from a database; determining an organ at risk (OAR) distance to target map, wherein the OAR distance to target map comprises distances to a target organ for respective portions of at least one OAR, and wherein the OAR distances are determined from at least one segmented patient organ image; selecting and downloading a cohort average dose distance to target histogram from the database; assigning a dose value to each of the portions of the at least one OAR to form a first 3D dose distribution map, wherein the assigned dose values are from the selected cohort average dose distance to target histogram; determining a second 3D dose distribution map based on a field arrangement determined by the selected treatment type and the first 3D dose distribution map; and calculating a dose distance to target histogram for the patient using the second 3D dose distribution map and the distance to target map.