In the treatment of a tumor with radiation therapy is enhanced by a weak magnetic field, the field strength time sequence of exposure and shape and contour of the magnetic field are varied to achieve desired results. In one separate aspect, exposure to a magnetic field is continued after exposure to a free radical-creating therapy is ceased or diminished, thereby increasing the lifetimes of free radicals which have already been created. In another preferred embodiment a magnetic field is strategically placed to avoid extending the lives of free radicals in tissue through which a free radical-creating beam must pass, to reach a tumor. This application discloses quantitative parameters for field strength and exposure time to create concentrations and reactivity of free radicals, including long-lived free radicals and discloses the use of shaped, contoured, and designed electromagnetic fields. A treatment planning station is also disclosed.