Hippocampal dosimetry and hippocampus sparing volumetric modulated arc therapy in patients with loco-regionally advanced oropharyngeal cancer

The hippocampus (HC) is a highly radiosensitive organ. Recent animal studies have shown that the radiation dose as low as 2 Gy can significantly impair the generation and maturation of the neuronal stem/progenitor cells and compromise the HC-dependent learning and memory. In this study, we aimed to evaluate the incidental radiation dose to the hippocampus in HPV-positive oropharyngeal cancer (OPC) patients who were treated with intensity modulated radiation therapy (IMRT). We also investigated the feasibility of IMRT plan optimization for HC sparing without compromising the target coverage and the dose constraints applied to the initial plan.