The combination of radiation therapy and immunotherapy for genitourinary cancer treatment: rationale, current evidence, and prospects

Targeted immunotherapy has emerged as a potentially effective systemic treatment for metastatic cancer in the past decade. However, a significant fraction of patients will either not respond or develop resistance to immunotherapy due to the immune-evasive properties of cancer. Radiation therapy can augment immunotherapy to modulate the immune suppressive tumor microenvironment and promote specific tumor targeting by the adaptive immune system. In this review, we will discuss the rationale for combining radiation therapy with immunotherapy and describe clinical studies using this combination strategy to improve the treatment response by inducing synergistic and abscopal effects. We will discuss ongoing prospective clinical trials that employ the combination of radiation therapy and immunotherapy in the treatment of genitourinary malignancies. Further advances in these combination therapy strategies are expected to improve the clinical response and disease course while further providing insight to the complex interactions and regulations between the immune system and cancer cells. Multiple additional clinical trials will be required to find routine application of this concept to the clinic.