1. A method for determining a radiation treatment plan for a patient, comprising: obtaining a reference plan, the reference plan including information regarding a reference region that has a different configuration from that of a region in the patient; using the reference plan to determine the treatment plan for the patient, wherein the treatment plan is determined using a processor; and storing the treatment plan; wherein the reference plan includes data regarding a reference dose distribution, and the act of using the reference plan comprises deforming the reference dose distribution to fit the region in the patient; and wherein the reference plan is for a different patient.