Introducing the periventricular region as a novel organ at risk in proton treatment planning of gliomas


Introducing the periventricular region as a novel organ at risk in proton treatment planning of gliomas

Eulitz, J.; Raschke, F.; Troost, E. G. C.; Thiele, J.; Makocki, S.; Menkel, S.; Appold, S.; Enghardt, W.; Krause, M.; Lühr, A.

The periventricular region (PVR) has been shown to have an increased susceptibility to dose-dependent brain injury after proton therapy of gliomas (Eulitz 2019, Harrabi 2019). However, the PVR has not been considered in proton treatment planning so far. Here, we present an approach for incorporating the PVR as a novel organ at risk in proton treatment planning.

The PVR was defined as a 4 mm uniformly expanded margin around the ventricular system. The PVR tolerance dose was estimated as the observed near-min dose derived within late post-treatment radiation-associated contrast-enhancements (CE) on T1wCE-follow up images. All grade II/III glioma patients treated between 2014 and 2018 with (adjuvant) proton radio(chemo)therapy to 54/60 Gy(RBE), respectively, were analyzed. Retrospective PVR-sparing treatment planning was performed for 11 (4/7) consecutive glioma patients (Fig.1). Patient-wise comparison to the clinically delivered plans considered the near-max dose D2% and the volume Vx that received more than x% of prescribed dose in PVR tissue outside the target boost volume.

The median distance of the observed CE lesion centers to the cerebral ventricles was 2.5 mm. The median and near-min CE lesion dose was 57.6 Gy(RBE) and 53.0 Gy(RBE), respectively. PVR-sparing treatment planning reduced D2% and V90% by 4.3 (±1.4)% and 53.2 (±22.4)%, respectively, while maintaining clinical goals (Fig.1).

PVR-sparing in treatment planning is a promising approach to reduce late brain injury. In many cases this should be possible without compromising target coverage and field homogeneity. Further experience will improve the arrangement of PVR-sparing in the priority order of planning goals.

Keywords: Proton Therapy; Gliomas; Periventricular Region

  • Contribution to proceedings
    PTCOG - 59th Annual Conference of the Particle-Therapy Co-operative Group, 09.-14.05.2020, Taipei, Taiwan

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Publ.-Id: 30042