Local treatment of unresectable tumors is challenging, particularly with radioactivity. Current practice relies on external beam irradiation or on a variety of medical devices for brachytherapy. Both approaches proved useful in controlling tumor growth but are characterized by poor patient's compliance, significant side effects, high costs and technological complexity hampering wide-spread use. The use of AvidinOX for radionuclide therapy of inoperable cancer lesions will offer a number of advantages compared to current brachytherapy. In fact, the perfusion of a target tissue with AvidinOX, compared to current devices, will allow adapting the therapy to the tumor/organ shape, and it will also make it possible to delay the administration of radioactivity for several days which, according to pre-clinical studies, might be also divided up into repeated doses. AvidinOX linking stably to tissue proteins, does not exhibit the problem of seed migration which is associated with high morbidity. Based on previous findings with AvidinOX in combination with radionuclides in pre-clinical studies as well as data from the clinical use in liver metastases, it can be assumed that intralesional injections of AvidinOX followed by intravenous injections of 177Lu-ST2210 could be a safe and efficacious method for treating inoperable tumor lesions.