A positioning device (1) for treating the inner walls of a resection cavity, which was created by surgically removing of at least a portion of a tumor in a living body, characterized by the fact that the material of the device (1), part(s) of the device and accessories of the device (1) is (are) biologically degradable in the living body. Further a surgical procedure for treating a tumor in a living body of at least one of the former claims, comprising: (a) surgically removing at least a portion of said tumor thereby creating a cavity in the living bodys remaining tissue (b) placing a biodegradable treatment device in said cavity so that the degradable device occupies said cavity and (c) treating tissue surrounding said cavity by means of said positioning device.
