Automated Contouring and Planning for Hippocampal-Avoidant Whole-Brain Radiotherapy

Abstract

Whole-brain radiotherapy (WBRT) remains an important treatment for over 200,000 cancer patients annually. Radiation dose to hippocampi predicts neurocognitive dysfunction. Hippocampal-avoidant WBRT (HA-WBRT) reduces neurocognitive toxicity compared to standard WBRT, but HA-WBRT contouring and planning are more complex and time-consuming than standard WBRT. We hypothesize that automated hippocampal segmentation and treatment planning can generate clinically acceptable HA-WBRT plans. We identified 40 consecutive patients with available MRI treated at one institution for brain metastases outside the hippocampal region. Each patient’s T1 post-contrast brain MRI was processed using FDA-approved software that can provide segmentations of brain structures in 5-7 minutes. Automated hippocampal segmentations were reviewed for accuracy and edited manually if necessary. These were converted to files compatible with a commercial treatment planning system, where hippocampal avoidance regions and planning target volumes (PTV) were generated. Other organs-at-risk (OARs) were previously contoured per clinical routine. A semi-automated knowledge-based planning routine was applied for a prescription of 30 Gy in 10 fractions using volumetric modulated arc therapy (VMAT) delivery. Plans were evaluated based on NRG-CC001 dose-volume objectives. Hippocampus segmentations were acceptable for 39 (97.5%) cases, with 1 case requiring minor manual editing. Automated plans had acceptable NRG-CC001 dose-volume objectives for PTV and OARs in 40 (100%) plans. Forty (100%) plans met PTV goals per protocol. For comparison, only 66.0% of plans on NRG-CC001 met PTV goals per protocol, with 26.3% within acceptable variation. In this study, 15 (37.5%) plans met OAR constraints per protocol and 25 (62.5%) were within acceptable variation, compared to 42.9% and 48.6% on NRG-CC001, respectively. No plans in our study had unacceptable dose to OARs, compared to 0.8% of manually generated plans from NRG-CC001. The median time for semi-automated planning was 9 minutes (range 7-13.5). A robust, semi-automated pipeline can generate clinically acceptable VMAT HA-WBRT plans in 15-20 minutes (plus time required to contour optic structures), without manual refinement of hippocampi in 97.5% of cases. This pipeline could improve clinical efficiency for a treatment proven to improve patient outcomes over standard WBRT.Tabled 1Abstract 2672; Table; Dose volume histogram for semi-automated HA-WBRTAutomated HA-WBRT Median (range)NRG-CC001Per ProtocolAcceptable VariationPTV D2% (Gy)34.3 (33.3-37.2)< 37.537.5-40PTV D98% (Gy)26.5 (25.5-28.8)> 2522.5-25PTV V30Gy (%)95 (95-95)> 9590-95Hippocampi D100% (Gy)8.1 (7.4-9.1)< 99-10Hippocampi Dmax (Gy)13.2 (9.7-15.7)< 1616-17Optic Nerves Dmax (Gy)29.9 (15.4-32.3)< 3030-37.5Optic Chiasm Dmax (Gy)30.2 (29.2-32.0)< 3030-37.5 Open table in a new tab