ESTRO 2024 - Abstract Book

S2137

Clinical - Upper GI

ESTRO 2024

4. Venkatesulu B, Giridhar P, Pujari L, Chou B, Lee JH, Block AM, Upadhyay R, Welsh JS, Harkenrider MM, Krishnan S, Verma V, En Hsieh C, Pradhan S, Small W, Jr., Solanki AA. Lymphocyte sparing normal tissue effects in the clinic (LymphoTEC): A systematic review of dose constraint considerations to mitigate radiation-related lymphopenia in the era of immunotherapy. Radiother Oncol. 2022;177:81-94.

5. R Core Team (2022). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria.

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Digital Poster

Comparative analysis of HDR brachytherapy and MR-guided SBRT of colorectal liver metastases

Svenja Hering 1 , Jan Hofmaier 1 , Maya Rottler 1 , Helmut Weingandt 1 , Sebastian Marschner 1 , Paul Rogowski 1 , Franziska Walter 1 , Claus Belka 1,2,3 , Stefanie Corradini 1 , Chukwuka Eze 1 1 LMU University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany. 2 German Cancer Consortium (DKTK), DKFZ and LMU University Hospital Munich, Munich, Germany. 3 Bavarian Cancer Research Center (BZKF), Bavarian Cancer Research Center (BZKF), Munich, Germany

Purpose/Objective:

Stereotactic body radiotherapy (SBRT) and high-dose-rate brachytherapy (BT) are treatment options in the local ablative treatment of colorectal liver metastases (CRLM). Previously, our group reported improved target volume dose coverage and reduced uninvolved liver exposure of high-dose-rate (HDR) interstitial BT vs. multi-fraction LINAC-based SBRT. Real-time MR-guided SBRT (MRgSBRT) is a relatively novel treatment technique allowing for superior tumour visualisation, anatomical plan adaption, and continuous tumour gating with initial studies indicating excellent target volume coverage and organs at risk (OARs) sparing in different tumor entities including liver tumours. The current study aimed to compare the plan quality and dosimetric parameters of single-fraction (SF) MR-guided intensity modulated radiation therapy (IMRT)/SBRT plans to that of delivered SF HDR-BT plans for colorectal liver metastases.

Material/Methods:

In total, 26 patients with 45 CRLM treated in 28 sessions with 1 x 25 Gy HDR-BT were retrospectively selected for the study. For each patient a “virtual” MRgSBRT plan was generated using the identical BT CT image set and structures. However, the planning target volumes (PTV SBRT ) for the MRgSBRT plans were generated with addition of an isotropic GTV expansion of 5 mm on the MRIdian treatment planning system (ViewRay Inc, Oakwood Village, USA). A prescription dose of 1 x 25 Gy (biologically effective dose, assuming an α/β -ratio of 10, BED 10 = 87.5 Gy 10 ) was delivered to the GTVs for BT plans and 1 x 25 Gy prescribed with the 80% isodose line covering the PTVs were generated for MRgSBRT plans. All plans were normalised to cover 95% of the PTV volume with 100% of the prescription dose (PTV D 95% = prescribed dose). We compared the dosimetric properties of delivered HDR-BT and MRgSBRT plans. We assessed the GTV BT/SBRT and PTV SBRT coverage and the uninvolved liver/OARs exposure.