Brain plasticity is fascinating and important to our life. Radiation therapy can cause brain injury which may cover or progress, posing an ideal case to study brain plasticity. We used a rare and unique cohort of nasopharyngeal carcinoma patients with normal-appearing brains to study irradiation injury in its preclinical stage in context of brain functional and structural plasticity. We found an acute increase in local brain activity, followed by its extensive reduction; and significant functional connectivity loss in the default mode network. Such radiosensitive functional alterations were intriguingly found to be plastic. By contrast, a progressive late disrupted integrity of the related white matter was starting to be significant after one year at the far end. Early increased local brain functional activity was able to predict severe later brain necrosis through a bridge of brain connectome. These findings highlight the importance of brain connectomics in translational clinical study.