Our study has several limitations. First, the study population was heterogeneous because we compared the NCF of patients who had undergone different WBRT fractionation schedules; Second, the small sample size made it difficult to elucidate possible confounders with a multivariate analysis; Finally, the degree of radiation-induced NCF deterioration might be overestimated, because it was difficult to eliminate the effect of the regrowth of intracranial tumors.