Background. During the clinical course of patients with locoregionally advanced non-small-cell lung cancer (LA-NSCLC) who have undergone aggressive treatment, brain metastasis (BM) is a frequent seen pattern of disease relapse, which cannot be ignored. It still remains unresolved whether prophylactic cranial irradiation (PCI) via whole brain radiotherapy (WBRT) should be recommended for NSCLC patients with stage III or pathologically nodal positive disease. Actually, PCI would significantly decrease the incidence of BM; however, potential WBRT-related neurocognitive function (NCF) sequelae are indeed a concern, which has made PCI seldom applied in clinical practice. In terms of the time course of WBRT-induced NCF decline, it might vary considerably according to the specific domains which are selected to be measured. Early neurocognitive decline principally involve impairments of episodic memory, which has been significantly associated with functions of the hippocampus. This study thus aims to explore the impact of PCI on the subsequent risk of developing BM and the multi-domain neurobehavioral functions in our eligible patients. Methods. Potentially eligible subjects are postoperative NSCLC patients with a status of pathologically nodal metastasis (pN+). Patients randomly assigned to the PCI arm will undergo the course of hippocampal-sparing PCI after they complete the fourth course of adjuvant platinum-based chemotherapy. Radiotherapy dose will be 3000 cGy in 15 fractions during three weeks. Except for the administration of hippocampal-sparing PCI, patients assigned to the observation arm should receive the same baseline and follow-up brain imaging examinations and neurocognitive assessments as those in PCI arm. Accordingly, a battery of neuropsychological measures, which includes 7 standardized neuropsychological tests (e.g., executive functions, verbal \& non-verbal memory, working memory, and psychomotor speed), is used to evaluate neurobehavioral functions for our registered patients. Expected results. This randomized controlled study aims to verify that the incidence of BM still can significantly be reduced by hippocampal-sparing PCI; additionally, NCF preservation regarding neurobehavioral assessments might also be achieved by hippocampal-sparing PCI as compared with the observation arm without PCI. No matter what the final results present, it is believed that this randomized controlled trial (RCT) will provide us solid evidence concerning the exact value of hippocampal-sparing PCI in our patient setting.