Targeting Stereotactic Body Radiotherapy on Metabolic PET- and Immuno-PET-Positive Vertebral Metastases.

Area of Science:

• Oncology
• Radiotherapy
• Nuclear Medicine

Background:

• Stereotactic body radiotherapy (SBRT) for vertebral metastases (VM) requires precise tumor targeting to spare the spinal cord.
• Accurate delineation of the clinical target volume (CTV) is crucial for effective SBRT.
• Current imaging modalities may not fully capture the extent of VM.

Purpose of the Study:

• To evaluate a novel approach for CTV delineation in VM using anti-carcinoembryonic antigen (CEA) positron emission tomography (pretargeted immuno-PET; iPET).
• To assess the impact of iPET on CTV delineation for SBRT in patients with metastatic breast cancer (BC) or medullary thyroid cancer (MTC).

Main Methods:

• Patients with VM underwent iPET, spine MRI, and PET-CT (using 18F-deoxyglucose or 18F-dihydroxy-phenylalanine).
• Vertebral lesion locations and segments were recorded.
• The impact of iPET-based delineation on MRI-based CTV was evaluated.

Main Results:

• Forty-six VM in eight patients were analyzed.
• iPET detected more vertebral segments (70) compared to MRI (81) and conventional PET/CT (26).
• iPET-based CTV delineation modified the MRI-based CTV in 70% of cases.

Conclusions:

• iPET provides precise mapping of affected VM segments, offering complementary information to MRI.
• This technique enhances the definition of target volumes for VM SBRT.
• iPET shows promise in improving treatment planning for stereotactic body radiotherapy in metastatic vertebral disease.