A method of image-guided radiotherapy for treatment of a radio-resistant or radio-sensitive tumor. A three-dimensional visualized tumor image is obtained and the boundary of the tumor is identified. A boosted radiation dose of treatment is designated and applied to a boost region within the tumor boundary. A predetermined prescribed radiation dose is simultaneously applied with the boosted radiation dose within the tumor boundary and in a planning target volume region, which is outside of the tumor boundary. The boosted radiation dose outside of the boost region decreases at a boost dose decreasing rate such that the boosted radiation dose is equal to the predetermined prescribed radiation dose at the tumor boundary.