Biological Principles of Stereotactic Body Radiation Therapy (SBRT) and Stereotactic Radiation Surgery (SRS): Indirect Cell Death

Purpose: To review the radiobiological mechanisms of stereotactic body radiation therapy stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS). Methods and Materials: We reviewed previous reports and recent observations on the effects of high-dose irradiation on tumor cell survival, tumor vasculature, and antitumor immunity. We then assessed the potential implications of these biological changes associated with SBRT and SRS. Results: Irradiation with doses higher than approximately 10 Gy/fraction causes significant vascular injury in tumors, leading to secondary tumor cell death. Irradiation of tumors with high doses has also been reported to increase the antitumor immunity, and various approaches are being investigated to further elevate antitumor immunity. The mechanism of normal tissue damage by high-dose irradiation needs to be further investigated. Conclusions: In addition to directly killing tumor cells, high-dose irradiation used in SBRT and SRS induces indirect tumor cell death via vascular damage and antitumor immunity.

Automated summary

High-dose irradiation in SBRT and SRS induces tumor cell death through vascular damage and increased antitumor immunity, in addition to direct tumor cell killing. Additional research is needed to further investigate the mechanisms of normal tissue damage caused by high-dose irradiation.