Heterogeneous intratumor irradiation: a new partner for immunotherapy.

We recently demonstrated that a heterogeneous tumor irradiation strategy, combining high-dose and low-dose radiotherapy (RT) within the same tumor volume, can synergize with immunotherapy in mice. Our findings indicate that heterogeneous RT doses may promote the spatial diversification of the antitumor immune response. Spatial fractionation of the RT dose has the potential to enhance the therapeutic index of RT/IO combinations, particularly in scenarios where irradiating the entire tumor volume is unfeasible or excessively harmful to the patient.