ESTRO 2023 - Abstract Book

S537

Sunday 14 May 2023

ESTRO 2023

calculated for DVH points with significant p-values (p < 0.05) and were 1.003 and 1.009 for left atrium D0.1cc and right lung Dmedian respectively. This correlates any dose to the left atrium with worse overall survival.

Substantial heart dose might not occur in every lung cancer radiotherapy treatment. Verifying the occurrence in this cohort was done by creating a histogram of D0.1cc and Dmedian of the whole heart (See Figure 1). This shows a Dmedian above 10 Gy for 11.8% of the patients, while nearly 2/3rd of the included patients has their D0.1cc above 10 Gy.

Conclusion Using a set of AI-generated CS contours, and thus avoiding uncertainty associated with deformable dose warping, we showed significant correlation between dose to the right lung and left atrium and survival in a large lung cancer cohort. In future work, we will extend this study to include other cardiac substructures.

Poster Discussion: CNS

PD-0645 A feasibility trial of preoperative radiosurgery for resectable brain metastases (PREOP-1) S. Rogers 1 , L. Schwyzer 2 , N. Lomax 3 , S. Alonso 4 , T. Lazeroms 5 , S. Schwenne 6 , G. Silvia 1 , S. Berkmann 2 , A. Tortora 7 , S. Marbacher 2 , G. Schubert 8 , O. Riesterer 9 1 Kantonsspital Aarau , Radiation Oncology Center KSA-KSB, Aarau , Switzerland; 2 Kantonsspital Aarau , Department of Neurosurgery , Aarau , Switzerland; 3 Kantonsspital Aarau, Radiation Oncology Center KSA-KSB, Aarau , Switzerland; 4 Kantonsspital Aarau , Radiation Oncology Centre KSA-KSB, Aarau , Switzerland; 5 Kantonsspital Aarau, Radiation Oncology Centre KSA-KSB, Aarau, Switzerland; 6 Kantonsspital Aarau , Radiation Oncology Center KSA-KSB, Aarau, Switzerland; 7 Kantonsspital Aarau , Department of Neurosurgery, Aarau, Switzerland; 8 Kantonsspital Aarau , Department of Neurosurgery , Aarau, Switzerland; 9 Kantonsspital Aarau , Radiation Oncology Centre KSA-KSB, Aarau, Switzerland Purpose or Objective Retrospective reports of preoperative radiosurgery for brain metastases (BMs) describe high efficacy with minimal toxicity. We present an interim analysis of a feasibility trial of radiosurgery prior to neurosurgical resection of a BM. Materials and Methods Eligibility criteria included: a BM up to 4 cm in diameter and up to three other BMs for radiosurgery, anticipated gross tumour resection, an estimated prognosis of at least six months and no contraindication to steroids or MRI. The date for elective neurosurgical resection was set following the tumour board and single fraction radiosurgery could be delivered up to and including the day of surgery. BMs were contoured on a 1.5T planning T1_Gd VIBE MRI and a 1mm planning treatment margin was added. The single fraction dose was prescribed according to PTV volume and prescribed to cover 99% of the PTV with a maximum dose between 125% and 143%. Treatment plans were generated using Elements Cranial SRS v1.5 and v3.0 (Brainlab, Germany). Treatment was delivered on a Truebeam STx linac using the Novalis Radiosurgery platform (Brainlab/Varian, USA). Patients completed EORTC QLQ-C30 and BN20 quality of life questionnaires at 0,3,6,9 and 12 months. An exploratory endpoint was the evaluation of any difference in expression of proliferative, histiocytic and immune cell markers between the primary tumours and the BMs.

Results