Results of the computational model for 4-Gy whole-brain irradiation are shown with the experimental results when the irradiation was delivered at 5 days after tumor-cell injection (PCI, for prophylactic cranial irradiation) (A) or at 3 weeks after tumor-cell injection (B). Explicit comparisons are made for the incidence of brain metastasis, the average number of metastases per mouse, and the tumor burden per mouse (upper quartile [UQ], median, and lower quartile [LQ]), in each case normalized to the corresponding 0-Gy control. In the PCI condition, the model consistently underestimated the effect of the 4-Gy dose on the experimental endpoints. Error bars indicate standard error of the mean.