Prophylactic cranial irradiation (PCI) is an important treatment modality of patients with limited stage small cell lung cancer (LD-SCLC). However, PCI is also associated with several side effects, such as decline in memory and other cognitive functions. This provides the rationale to explore the clinical feasibility of hippocampal avoidance during WBRT. Previous studies have demonstrated the dosimetric capabilities of IMRT to conformally avoid the hippocampus without detriment to the radiation dose the remaining brain receives. The aims of this study is to evaluate the therapy efficacy and the safety profile of hippocampal-sparing whole-brain radiation therapy (HS-WBRT) for PCI in patients with LD-SCLC.