Immunotherapy and Stereotactic Body Radiation Treatment—An Overview of the Current Landscape of the Strategic Combination of Two Treatment Modalities to Achieve Better Therapeutic Outcomes

Radiation plays an important role in the treatment of many solid tumors. While conventional fractionation schedules are commonly used, technological advances have allowed safer and more effective dose escalation in the treatment of both primary as well as metastatic lesions. There is growing evidence about the intricate role played by the immune system in modulating the effect of cancer treatment, and several pre-clinical and clinical studies have explored the use of immunotherapy in the treatment of various cancers, both in the metastatic and upfront treatment setting. This approach has shown significant success in the management of melanomas and lung cancers and has prompted exploration of the same strategy in many other cancer subtypes. Radiation has been proposed to synergize the effect of immunotherapy through various mechanisms and is currently being evaluated in various ongoing clinical trials. Several mature clinical studies have also shown significant benefit with the combination and have led to its uptake in routine clinical practice. Furthermore, the use of hypo-fractionated high-dose radiation or Stereotactic Body Radiation Treatment (SBRT) regimens have shown benefits over conventional radiation in this context and are being actively explored as a treatment strategy.