Finally, a new neural network system for breast cancer treatment planning was developed. As plans for breast cancer treatments differ greatly from plans for abdominal cancer treatments, a new network architecture was required. The system developed has again been tested on clinical planning tasks at Royal Berkshire Hospital and results show that, in some cases, plans which improve on those produced by the hospital are generated. The remainder of this chapter is set out as follows. Section 13.2 provides background in the domain of radiation therapy. This is necessary to set the context in which the evolutionary neural network operates, and to gain an appreciation of the choices of input and output coding and other parameters. Section 13.3 reviews and discusses evolutionary algorithm training of neural networks. Section 13.4 then describes our application of evolutionary neural networks to the radiotherapy of abdominal cancer and breast cancer. Section 13.5 concludes and summarises the chapter, and discusses future work.