ESTRO 2025 - Abstract Book

S730

Clinical - CNS

ESTRO 2025

Results:

Relevant comparisons between generated and available contours are summarized in Table 1.

A summary of cases where there was more significant over-contouring vs. under-contouring is detailed in Table 2.

Conclusion: Consideration of both the DICE coefficient analysis as well as the over-/under-contouring analysis led to the following conclusions: 1. Clinical Hippo and PRV contours generally have DICE of 0.62-0.65 and 0.81-0.82 when compared to the STAPLE which defines a level of acceptability when assessing auto-generated contours. 2. Limbus MRI contours are a clinically acceptable surrogate due to their DICE of 0.65-0.68 (hippo) and 0.81-0.84 (PRV); whereas CT-based Limbus contours are slightly inferior– 0.56-0.58 (hippo) 0.77-0.79 (PRV). 3. Limbus CT-based auto-contours are consistently over-contoured when compared to STAPLE, MR Limbus, and clinically delivered contours. Therefore, Limbus CT-based auto-contours can be used clinically with the understanding that this may lead to more brain sparing near the hippocampi. Given that known brain metastases near hippocampal structures is a contraindication for HA-WBRT, CT-based auto-contours without the use of MR imaging is a reasonable alternative care path, particularly in resource-constrained practice environments. References: 1. Patchell RA, et al. Postoperative radiotherapy in the treatment of single metastases to the brain: a randomized trial. JAMA. 1998;280(17):1485-9. 2. Chang EL, et al. Neurocognition in patients with brain metastases treated with radiosurgery or radiosurgery plus whole-brain irradiation: a randomised controlled trial. Lancet Oncol. 2009;10(11):1037-44. 3. Leskinen S, et al. Hippocampal avoidance in whole brain radiotherapy and prophylactic cranial irradiation: a systematic review and meta-analysis. J Neurooncol. 2023;163(3):515-527. 4. Brown PD, et al. Hippocampal avoidance during whole-brain radiotherapy plus memantine for patients with brain metastases: Phase III Trial NRG Oncology CC001. J Clin Oncol. 2020;38(10):1019-1029. Keywords: auto-contouring, WBRT, AI