Safely delivering doses to tumors and improving local control is one of the consequences of the development of advanced 3D radiotherapy planning. Increasing precision also leads to sparing dose to healthy tissues thus increasing the quality of life. The main goal of all radiotherapy treatments is to deliver radiation to PTV as planned. Portal imaging upon treatment session can increase confidence of this occurrence but despite patient positioning and immobilization the desired dose may be prevented from being delivered. In fact, during the treatment the position and dimension of the tumor may vary consistently due to organs movements and mass reduction.