ORIGINAL ARTICLE: Sparing of the hippocampus and limbic circuit during whole brain radiation therapy: A dosimetric study using helical tomotherapy

Marsh, J. W.; Gielda, BT; Herskovic, AM; Wendt, Julie; Turian, JV

doi:10.1111/j.1754-9485.2010.02184.x

Cited by 30 publications

(26 citation statements)

References 26 publications

(35 reference statements)

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“…Comparisons of limbic sparing experimental plans were conducted in 11 patients indicated for WBRT and for PCI. Similar reduction of hippocampal biological equivalent doses was achieved for both of these clinical situations [51,52]. These results are not surprising considering the fact, that PCI differ from WBRT only in terms of fractionation and that the standard radiotherapy technique is similar.…”

Section: Introductionsupporting

confidence: 74%

“…On the other hand, for HA PBRT, where only the contralateral hippocampus is often spared, it is possible to contour the whole hippocampus irrespective of its NSCs rich part according to a radiation oncologist’s guide to contouring the hippocampus proposed by Chera et al [56]. Moreover, considering an attempt to spare NCF during brain irradiation, some studies defined OARs even more comprehensively including the whole limbic circuit (whole hippocampus; the rest of limbic circuit comprising the amygdalar complex, the fornix, the cingulum, the cingulated gyrus, and the mammillary bodies) [38,51]. …”

Section: Introductionmentioning

confidence: 99%

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Why and how to spare the hippocampus during brain radiotherapy: the developing role of hippocampal avoidance in cranial radiotherapy

et al. 2014

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The goal of this review is to summarize the rationale for and feasibility of hippocampal sparing techniques during brain irradiation. Radiotherapy is the most effective non-surgical treatment of brain tumors and with the improvement in overall survival for these patients over the last few decades, there is an effort to minimize potential adverse effects leading to possible worsening in quality of life, especially worsening of neurocognitive function. The hippocampus and associated limbic system have long been known to be important in memory formation and pre-clinical models show loss of hippocampal stem cells with radiation as well as changes in architecture and function of mature neurons. Cognitive outcomes in clinical studies are beginning to provide evidence of cognitive effects associated with hippocampal dose and the cognitive benefits of hippocampal sparing. Numerous feasibility planning studies support the feasibility of using modern radiotherapy systems for hippocampal sparing during brain irradiation. Although results of the ongoing phase II and phase III studies are needed to confirm the benefit of hippocampal sparing brain radiotherapy on neurocognitive function, it is now technically and dosimetrically feasible to create hippocampal sparing treatment plans with appropriate irradiation of target volumes. The purpose of this review is to provide a brief overview of studies that provide a rationale for hippocampal avoidance and provide summary of published feasibility studies in order to help clinicians prepare for clinical usage of these complex and challenging techniques.

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Section: Introductionsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Why and how to spare the hippocampus during brain radiotherapy: the developing role of hippocampal avoidance in cranial radiotherapy

et al. 2014

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“…Better sparing of normal brain tissue has been accomplished with IMSRT substituting 3D conformal dose escalated radiotherapy for high grade glioma with a consecutively reduced normal tissue complication probability in a radiobiological modelling study [31]. In patients requiring whole brain irradiation due to brain metastases, IMSRT has been shown to better spare the hippocampus both by linac based technique as well as by tomotherapy, when these organs at risk have been subjected to a high penalty in the inverse optimization algorithm [14,32,33]. …”

Section: Discussionmentioning

confidence: 99%

Neural stem cell sparing by linac based intensity modulated stereotactic radiotherapy in intracranial tumors

et al. 2013

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BackgroundNeurocognitive decline observed after radiotherapy (RT) for brain tumors in long time survivors is attributed to radiation exposure of the hippocampus and the subventricular zone (SVZ). The potential of sparing capabilities for both structures by optimized intensity modulated stereotactic radiotherapy (IMSRT) is investigated.MethodsBrain tumors were irradiated by stereotactic 3D conformal RT or IMSRT using m3 collimator optimized for PTV and for sparing of the conventional OARs (lens, retina, optic nerve, chiasm, cochlea, brain stem and the medulla oblongata). Retrospectively both hippocampi and SVZ were added to the list of OAR and their dose volume histograms were compared to those from two newly generated IMSRT plans using 7 or 14 beamlets (IMSRT-7, IMSRT-14) dedicated for optimized additional sparing of these structures. Conventional OAR constraints were kept constant. Impact of plan complexity and planning target volume (PTV) topography on sparing of both hippocampi and SVZ, conformity index (CI), the homogeneity index (HI) and quality of coverage (QoC) were analyzed. Limits of agreement were used to compare sparing of stem cell niches with either IMSRT-7 or IMSRT-14. The influence of treatment technique related to the topography ratio between PTV and OARs, realized in group A-D, was assessed by a mixed model.ResultsIn 47 patients CI (p ≤ 0.003) and HI (p < 0.001) improved by IMSRT-7, IMSRT-14, QoC remained stable (p ≥ 0.50) indicating no compromise in radiotherapy. 90% of normal brain was exposed to a significantly higher dose using IMSRT. IMSRT-7 plans resulted in significantly lower biologically effective doses at all four neural stem cell structures, while contralateral neural stem cells are better spared compared to ipsilateral. A further increase of the number of beamlets (IMSRT-14) did not improve sparing significantly, so IMSRT-7 and IMSRT-14 can be used interchangeable. Patients with tumors contacting neither the subventricular zone nor the cortex benefit most from IMSRT (p < 0.001).ConclusionThe feasibility of neural stem cell niches sparing with sophisticated linac based inverse IMSRT with 7 beamlets in an unselected cohort of intracranial tumors in relation to topographic situation has been demonstrated. Clinical relevance testing neurotoxicity remains to be demonstrated.

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“…Indeed, overall neurocognitive benefit has been claimed [25], as well as the possibility of reducing harm by sparing portions of the brain [26,27].…”

Section: Distant Intracranial Controlmentioning

confidence: 99%

Image-guided stereotactic radiotherapy of the resection cavity for single resectable brain metastases

Badakhshi¹,

Lux²,

Kaul³

et al. 2014

Med Imaging Radiol

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Objectives: To determine if the postoperative delivery of fractionated stereotactic radiotherapy (FSRT) for resection cavity for patients with single and resectable brain metastases is safe and effective. Methods: A prospective feasibility protocol was set up to include patients with single and resectable brain metastases who underwent surgery and had low risk profile according to RPA classification. Fractionated stereotactic radiotherapy was applied. Single dose: 3.8 Gy, total dose: 41.8 or 49.6 Gy. Results: There was no case of break due to clinical problems. There was no case of delay of FSRT. The onset acute toxicity was observed in 40 cases (76.9%), no grade 3 and more was seen. Local recurrence free survival was 32.6 months, local control rate at 6, 12, 18 and 24 months were 85%, 77.9%, 65.9% and 65.9%. Overall local failure occurred in 34.1% of patients. Overall survival rates at 6, 12, 18 and 24 months were 90.3%, 63.9%, 47.7% and 31.6%. Median survival was 18.3 months (13.8-22.8) and overall 17.3% were living at the time of last analysis. Distant control rates at 6, 12, 18 and 24 months were 49.4%, 38.2%, 25.5% and 22.3%. Median distant recurrence free survival was 6 months (0-12.0) with overall distant failure in 77.7% of patients. Conclusion: FSRT for surgical cavity might be one possible option in treatment of single and resectable brain metastases.

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ORIGINAL ARTICLE: Sparing of the hippocampus and limbic circuit during whole brain radiation therapy: A dosimetric study using helical tomotherapy

Abstract: It is dosimetrically feasible to spare the hippocampus and the rest of the limbic circuit using helical tomotherapy while treating the rest of the brain to full dose.

Cited by 30 publications

References 26 publications

Why and how to spare the hippocampus during brain radiotherapy: the developing role of hippocampal avoidance in cranial radiotherapy

Why and how to spare the hippocampus during brain radiotherapy: the developing role of hippocampal avoidance in cranial radiotherapy

Neural stem cell sparing by linac based intensity modulated stereotactic radiotherapy in intracranial tumors

Image-guided stereotactic radiotherapy of the resection cavity for single resectable brain metastases

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