Multimodal treatment concepts of local radiation therapy with immunotherapy. Rationale for combination therapy and possible clinical treatment strategies

Immunotherapy has been established in the treatment of cancer in general and specifically in uro-oncology. The rationale to combine these therapies with radiotherapy is based on the biological effects of irradiation, which exceed the "physical" properties of irradiation to kill tumor cells. Depending on radiation dose and fractionation as well as tumor model or tumor entity used, irradiation can lead to immune stimulation or immune inhibition. As immune response is not limited to the local tumor microenvironment but occurs on a systemic level, a successful anticancer immune response after irradiation of one metastasis can lead to systemic tumor control (abscopal effect). Clinical trials test combination regimens in locally advanced tumors in the curative setting to improve survival rates and in the metastatic setting to prolong survival in palliative treatment. In addition, radiotherapy is used for local treatment of oligometastases and oligoprogression under palliative systemic therapy.