Department of Radiation Oncology, Saarland University Medical Center, Homburg, Saar, Germany.
Radiat Oncol. 2023 Apr 7;18(1):64. doi: 10.1186/s13014-023-02242-3.
The high susceptibility of the hippocampus region to radiation injury is likely the causal factor of neurocognitive dysfunctions after exposure to ionizing radiation. Repetitive exposures with even low doses have been shown to impact adult neurogenesis and induce neuroinflammation. We address the question whether the out-of-field doses during radiotherapy of common tumour entities may pose a risk for the neuronal stem cell compartment in the hippocampus.
The dose to the hippocampus was determined for a single fraction according to different treatment plans for the selected tumor entities: Point dose measurements were performed in an anthropomorphic Alderson phantom and the out-of-field dose to the hippocampus was measured using thermoluminescence dosimeters.
For carcinomas in the head and neck region the dose exposure to the hippocampal region for a single fraction ranged from to 37.4 to 154.8 mGy. The hippocampal dose was clearly different for naso-, oro- and hypopharynx, with maximal values for nasopharynx carcinoma. In contrast, hippocampal dose levels for breast and prostate cancer ranged between 2.7 and 4.1 mGy, and therefore significantly exceeded the background irradiation level.
The mean dose to hippocampus for treatment of carcinomas in the head and neck region is high enough to reduce neurocognitive functions. In addition, care must be taken regarding the out of field doses. The mean dose is mainly related to scattering effects, as is confirmed by the data from breast or prostate treatments, with a very different geometrical set-up but similar dosimetric results.
海马区对辐射损伤的高度敏感性可能是暴露于电离辐射后神经认知功能障碍的因果因素。即使是低剂量的重复暴露也已被证明会影响成年神经发生并引发神经炎症。我们提出了这样一个问题，即在常见肿瘤实体的放射治疗过程中外照射剂量是否会对海马体中的神经元干细胞区构成风险。
根据所选肿瘤实体的不同治疗计划，单次分割时确定海马体的剂量：在人体模型 Alderson 体模中进行点剂量测量，并使用热释光剂量计测量海马体的外照射剂量。
对于头颈部的癌症，海马区单次分割的剂量暴露范围为 37.4 至 154.8 mGy。对于鼻咽、口咽和下咽，海马剂量明显不同，鼻咽癌的剂量最大。相比之下，乳腺癌和前列腺癌的海马剂量水平在 2.7 至 4.1 mGy 之间，因此明显超过了背景照射水平。
治疗头颈部癌症的海马体平均剂量足以降低神经认知功能。此外，必须注意外照射剂量。平均剂量主要与散射效应有关，这从乳房或前列腺治疗的数据得到证实，尽管几何结构非常不同，但剂量学结果相似。
