Integration of ⁶⁸Ga-DOTA-TOC PET/CT into radiotherapy planning for intracranial meningiomas: A precision-imaging approach to tumor delineation

Abstract

Background

Accurate target delineation is critical for radiotherapy (RT) planning in intracranial meningiomas, particularly in complex anatomical regions such as the skull base or in postoperative settings. Meningiomas characteristically overexpress somatostatin receptor subtype-2 (SSTR2), allowing high-contrast molecular imaging with ⁶⁸Ga-DOTA-TOC PET/CT. This study evaluated the impact of integrating SSTR-PET with conventional imaging on RT target delineation in patients with intracranial meningiomas.

Methods

In this single-center observational study, 25 consecutive patients with intracranial meningioma undergoing radiotherapy planning underwent MRI and ⁶⁸Ga-DOTA-TOC PET/CT. Gross tumor volumes were delineated using MRI alone and PET-fused CT images. PET-derived biological tumor volume (BTV) was generated using a 40% SUVmax threshold. Semiquantitative PET parameters, SUVmax and tumor-to-background ratio (TBR), were recorded. Changes in GTV delineation following PET integration were analyzed.

Results

⁶⁸Ga-DOTA-TOC PET demonstrated intense SSTR expression (SUVmax 14.19 ± 10.88; TBRmax 83.48 ± 76.18) and precisely delineated tumor margins. PET identified osseous involvement in 40% of patients compared with 16% detected on MRI alone and revealed additional nonadjacent disease sites in 28% of cases. PET-based GTVs were significantly smaller than MRI-based volumes (12.01 ± 12.77 cm³ vs. 20.02 ± 18.71 cm³, p = 0.012). Integration of PET resulted in clinically relevant contour modification (> 5%) in 17 of 20 evaluable patients, including bone-specific adjustments in 12.

Conclusion

⁶⁸Ga-DOTA-TOC PET/CT demonstrated complementary value in radiotherapy planning for intracranial meningiomas, producing systematic geometric modifications in target volumes, with more frequent osseous involvement detection compared to MRI alone. These hypothesis-generating findings require validation in larger prospective multicenter studies with long-term clinical outcome endpoints before routine clinical adoption.