A system and method for interactive interstitial photo-dynamic tumour therapy and/or photothermal tumour therapy of a human or animal, said system comprising at least one radiation distributor, which is arranged for distribution of optical radiation from at least one radiation source to a reaction site, or from the reaction site to at least one radiation sensor. The radiation distributor comprises at least one translatory displacement element being translatory movable relatively to another element. First ends of first radiation conductors are fixed to the first translatory displacement element and first ends of second radiation conductors are fixed to the other element, wherein the first and the second radiation conductors are connectable to each other in different constellations through translatory movement of the translatory displacement element and the other element relative each other in order to obtain different operation modes of said system.