Stereotactic Ablative Radiotherapy (SABR): Impact on the Immune System and Potential for Future Therapeutic Modulation.

Stereotactic ablative radiotherapy (SABR) has been demonstrated to provide excellent local control in several malignancies. Recent reports have suggested that this ablative dose may impact disease outside of the radiated area. Furthermore, these studies have implicated immune modulation as the primary mechanism of disease response outside the irradiated area. More specifically, T-cell stimulation and tumor necrosis factor-α modulation following high dose irradiation have been suggested as the responsible components of this phenomenon. In addition, the "abscopal effect" may play a role in disease response outside of the radiated area. We review the current literature regarding the effects of ablative radiation therapy, the potential for immune modulation from it, and the mechanisms of the distant effects it elicits.