Longitudinal multimodal MRI monitoring of a novel combination therapy using radiosurgery and checkpoint inhibitor immunotherapy in glioblastoma multiforme

Multimodal MRI was used to longitudinally monitor the effects of a novel combination therapy of radiosurgery and programmed death-ligand 1 (PD-1) checkpoint inhibitor in a mouse model of GBM. We found that combination therapy of radiosurgery and immune checkpoint inhibition was more effective in reducing tumor volume and yielded better survival compared to non-treated, radiation-alone or immunotherapy-alone group. At 30-day post-treatment onset, tumor-ROI T2, apparent-diffusion coefficient, fractional anisotropy, and kurtosis of the combination treatment group were significantly different from those of the non-treated group (p<0.05). Immunohistochemical results further shed light on possible mechanisms of action.