1. A radiation treatment planning apparatus comprising: a processor configured to: generate a statistical model for a change in radiation therapy plan (RTP) data based on change data of RTP data collected in association with radiation therapy results data, wherein the change data of RTP data is based on a difference between a first previous RTP data before a previous radiation therapy at least associated with the radiation therapy results has been executed and a second previous RTP data after the previous radiation therapy has been executed, wherein the difference depends at least on a radiation therapy result resulted from the first previous RTP data; set first RTP data based on a medical image of a region of interest of a patient; acquire first radiation therapy results data resulting from the first RTP data; acquire statistical data corresponding to the first RTP data and the first radiation therapy results data from the statistical model; generate second RTP data using the statistical data and personalized data of the patient; and acquire second radiation therapy results data resulting from the second RTP data.