High incidence of pain during RT and RT-CT calls for increased awareness of the importance of pain monitoring and treatment during RT of OPC patients. The analgesic treatment had to be adjusted individually.
Radiotherapy (RT) is frequently used in the treatment of primary and secondary brain tumours, as well as in prophylactic cranial irradiation (PCI). The hippocampus plays a key function in the process of remembering, relaying information from short-term to long-term memory as consolidation, and spatial orientation. Sparing the hippocampus during brain radiotherapy aims to prevent hippocampal-dependent cognitive function deterioration.This procedure requires a good knowledge of the brain's radiological anatomy and use of modern radiotherapy techniques.This article presents the validity of hippocampus sparing during brain radiotherapy, the potential benefits of using this procedure, available clinical premises regarding patient qualification, and technical difficulties in the brain's RT planning with hippocampus avoidance.
Radiotherapy is one of the principal methods for treating brain cancer. Over recent years, a decline in patient quality of life has increasingly been observed in those undergoing brain irradiation, where hippocampal-dependent cognitive function has become impaired. The hippocampus is a paired structure of the limbic system situated in the medial temporal lobes of the telencephalon. Preliminary findings suggest that irradiation damaged neural stem cells in the hippocampus undergo apoptosis, resulting in deteriorating cognitive function. Despite the technical aspects for affording hippocampal avoidance during irradiation, much controversy still surrounds the techniques that shield the hippocampus without reducing the benefits of the intended radiotherapy for a given clinical condition. Furthermore, a tolerated radiation dose sufficient for preserving neural stem cell function has not been yet established. Delivering a method for an unequivocal assessment of cognitive function, post-irradiation, is also fraught with difficulty. Hitherto, only subjective psychological testing have been applied such as MMSE, HVLT or AVLT methods. Objective methods for optimally determining radiation-induced injury to the hippocampal region are still being investigated.
Hippocampal-sparing brain radiotherapy (HS-BRT) in cancer patients results in preservation of neurocognitive function after brain RT which can contribute to patients’ quality of life (QoL). The crucial element in HS-BRT treatment planning is appropriate contouring of the hippocampus. Ten doctors delineated the left and right hippocampus (LH and RH, respectively) on 10 patients’ virtual axial images of brain CT fused with T1-enhanced MRI (1 mm) according to the RTOG 0933 atlas recommendations. Variations in the spatial localization of the structure were described in three directions: right–left (X), cranio-caudal (Y), and forward–backward (Z). Discrepancies concerned three-dimensional localization, shape, volume and size of the hippocampus. The largest differences were observed in the first three delineated cases which were characterized by larger hippocampal volumes than the remaining seven cases. The volumes of LH of more than half of hippocampus contours were marginally bigger than those of RH. Most differences in delineation of the hippocampus were observed in the area of the posterior horn of the lateral ventricle. Conversely, a large number of hippocampal contours overlapped near the brainstem and the anterior horn of the lateral ventricle. The most problematic area of hippocampal contouring is the posterior horn of the lateral ventricle. Training in the manual contouring of the hippocampus during HS-BRT treatment planning under the supervision of experienced radiation oncologists is necessary to achieve optimal outcomes. This would result in superior outcomes of HS-BRT treatment and improvement in QoL of patients compared to without HS-BRT procedure. Correct delineation of the hippocampus is problematic. This study demonstrates difficulties in HS-BRT treatment planning and highlights critical points during hippocampus delineation.
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