Multiple tumors are grouped into multiple treatment groups. Tumors in different treatment groups are treated by a radiosurgery in different treatment sessions than the tumors in the same treatment groups. The tumors can be grouped so as to decrease the biologically effective dose received by normal tissue in the treatment area. The radiosurgical planning system can divide the tumors into groups based on their location relative to each other and the radiation the tumors will be treated with and create a plan for treating the tumors according to the treatment groups.