ESTRO 2024 - Abstract Book

S871

Clinical - CNS

ESTRO 2024

25 patients with WHO Grade I meningiomas of the skull base, who received [68Ga]-DOTATATE-PET/CT for radiation therapy planning, have been retrospectively included in this study.

In total, 4 radiation oncologists initially defined a Gross Tumor Volume (GTV) based on MRI (GTV MRI ), then based on the combined PET/CT information (GTV PET/CT ), and finally, a target volume considering both the MRI and PET/CT information (GTV all ). Within each modality, a consensus structure was generated by applying the Simultaneous Truth and Performance Level Estimation (STAPLE) algorithm using the CERR research planning system (GTV MRT,STAPLE , GTVP ET/CT,STAPLE , and GTV all,STAPLE ). The agreement among the 4 radiation oncologists for each modality was assessed using the Kappa statistic (-1=no agreement; +1=perfect agreement). The consensus structures from different modalities were compared with each other using the Sørensen – Dice similarity coefficient (DSC).

Results:

25 patients have been included, who were treated between 06/2012 and 01/2018 with a total dose of 50.4-54 Gy in 1.8 Gy per fraction. 17 patients were treated for recurrent/residual tumors following prior surgery, while 8 patients received definitive radiation therapy. All tumors were located in the skull base region. The agreement among radiation oncologists was on average κ=0.71 for GTV MRI , κ=0.67 for GTV PET/CT , and κ=0.75 for GTV all . The comparison of volumes GTV MRT,STAPLE and GTV PET/CT,STAPLE resulted in a mean DSC of 0.70, GTV MRT,STAPLE and GTV all,STAPLE DSC=0.84, and GTV PET/CT,STAPLE and GTV all,STAPLE DSC=0.83.

Conclusion:

The inclusion of [68Ga]-DOTATATE-PET/CT in radiation therapy planning for low-grade meningiomas results in a modification of the target volume compared to MRI-based planning alone. There is a good agreement in target volumes delineated by independent contouring physicians by adding of metabolic imaging.

Keywords: meningeoma, PET/CT, target volume definition

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