Dosimetry And Cognitive Function Observation Of Hippocampal-sparing Whole Brain Radiotherapy

Objective: In this study,the clinical feasibility of hippocampal-sparing technology was explored by reducing hippocampal dose in whole brain radiotherapy and observing the neurocognitive function damage after radiotherapy.Methods: From October 2018 to October 2019,patients with brain metastasis in Shaanxi Provincial Cancer Hospital were strictly screened,and 20 patients were finally included as subjects according to the inclusion and exclusion criteria.Shielding group(Observation group),10 patients were treated with hippocampal protective whole brain radiotherapy by volumetric-modulated arc therapy.In the unshielded group(control group),another 10 patients received conventional whole brain radiotherapyby dynamic intensity modulated radiotherapy.The volume and dose parameters of plan PTV,hippocampus,organs at risk and neurocognitive function score after treatment were compared between the two groups.Results: The comparison of PTV volume between the two groups,P=0.47,showed no statistical significance(P>0.05).Comparison of PTV uniformity index between the two groups,the shielding group and the unshielded group were 1.15±0.03 and 1.07±0.02,respectively,showing statistical significance(P=0.00).Conventional whole brain radiotherapy was superior to hippocampal protective whole brain radiotherapy in the dose uniformity of target area.The left and right hippocampal volumes of the two groups were compared(P=0.71,P=0.60),and the comparison was not statistically significant(P>0.05).Dmean and Dmax of the left and right hippocampus in the two groups(P = 0.00,P = 0.00),the comparison between two groups was statistically significant(P<0.05).Dmean and Dmax in the left hippocampus decreased to 34.69% and 51.37% of the prescription dose,and Dmean and Dmax in the right hippocampus decreased to 34.90% and 51.05% of the prescription dose,respectively.Dmean of planned left and right lens in the two groups(P =0.00;P = 0.00)and Dmax(P = 0.00),the comparison between two groups was statistically significant(P =0.00),and the unshielded group was superior to the shielding group in terms of lens irradiation dose.Comparison results of neurocognitive function scores,there was no statistical significance in comparison of neurocognitive function scores before,after and 1month after treatment between the two groups(P> 0.05).The comparison of 3 months after treatment between the two groups was statistically significant(P< 0.05).In the shielding group,there was statistically significant difference between before and after treatment and 1month after treatment(P< 0.05).In the unshielded group,there was no statistically significant difference between before and after treatment and 1 month after treatment(P>0.05).The scores of neurocognitive function before and 3 months after treatment were statistically significant(P< 0.05).The neurocognitive function score of the shielding group was better than that of the unshielded group.Conclusion: Compared with conventional whole brain radiotherapy,the use of hippocampal protective technique can significantly reduce the exposure dose to the hippocampus,ensure the dose coverage of the whole brain,and no obvious toxic and side effects have been observed,which has a certain protective effect on the cognitive function of patients.