Fig. 1.

Schematic overview of local effects triggered by partial tumor irradiation. At the heart of the primary tumor that is irradiated with high dose (in the middle), three effects can be distinguished: endothelial cells death and vasculature damage; induction of CD8 T cells and cell death signals release. Current evidence suggests that high dose radiation per fraction can induce immunosuppression on tumor edge while low dose radiation can induce immunomodulatory effect via neoantigen release, recruitment of CD8+ T cells to tumor edge and activation of IFN pathway genes.

As a result, partial tumor radiation is primed to attack tumors with high dose in the core and achieve a low dose radiation to tumor edge with rapid dose fall off. This strategy would potentially combine the inherent advantages of various fractionation schemes while avoiding the potential pitfalls of immunosuppressive effects rendered by high dose radiation to the whole tumor.