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

Baptiste Pichon,Matthieu Le Turnier,Caroline Bodet-Milin,Audrey Blanc-Lapierre,Caroline Rousseau,Ludovic Ferrer,Vincent Libois,David M Goldenberg,Gregory Delpon,Françoise Kraeber-Bodere,Cédric Lenoble,Stéphane Supiot

doi:10.3390/biomedicines8120548

Abstract

(1) Background: Stereotactic body radiotherapy (SBRT) for vertebral metastases (VM) allows the delivery of high radiation doses to tumors while sparing the spinal cord. We report a new approach to clinical target volume (CTV) delineation based on anti-carcinoembryonic antigen (CEA) positron emission tomography (pretargeted immuno-PET; “iPET”) in patients with metastatic breast cancer (BC) or medullary thyroid cancer (MTC). (2) Methods: All patients underwent iPET, spine magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT) using 18F-deoxyglucose (FDG) for BC or 18F-dihydroxy-phenylalanine (F-DOPA) for MTC. Vertebrae locations and vertebral segments of lesions were recorded and the impact on CTV delineation was evaluated. (3) Results: Forty-six VM eligible for SBRT following iPET were evaluated in eight patients (five BC, three MTC). Eighty-one vertebral segments were detected using MRI, 26 with FDG or F-DOPA PET/CT, and 70 using iPET. iPET was able to detect more lesions than MRI for vertebral bodies (44 vs. 34). iPET-based delineation modified MRI-based CTV in 70% (32/46) of cases. (4) Conclusion: iPET allows a precise mapping of affected VM segments, and adds complementary information to MRI in the definition of candidate volumes for VM SBRT. iPET may facilitate determining target volumes for treatment with stereotactic body radiotherapy in metastatic vertebral disease.

Highlights

Stereotactic body radiation therapy (SBRT) has emerged as a treatment option for selected patients with vertebral metastases (VM), with the objectives of pain-relieving decompression, tumor stabilization, and preventionBiomedicines 2020, 8, 548; doi:10.3390/biomedicines8120548 www.mdpi.com/journal/biomedicinesBiomedicines 2020, 8, 548 of fractures [1,2]
The consensus recommendations suggest that the clinical target volume (CTV) should include abnormal marrow signals suspicious for microscopic invasion and an adjacent normal bony expansion to account for subclinical tumor spread
Functional imaging using positron emission tomography combined with computed tomography (PET/CT) using, for example, 18 fluorodeoxyglucose (FDG) has been developed with the objective of improving diagnostic precision for the detection of bone metastases, with a good sensitivity and specificity except for lesions measuring less than 10 mm [7]

Summary

Introduction

Stereotactic body radiation therapy (SBRT) has emerged as a treatment option for selected patients with VM, with the objectives of pain-relieving decompression, tumor stabilization, and preventionBiomedicines 2020, 8, 548; doi:10.3390/biomedicines8120548 www.mdpi.com/journal/biomedicinesBiomedicines 2020, 8, 548 of fractures [1,2]. A promising option to improve diagnostic imaging has been immuno-PET, which combines the high sensitivity of PET with the specificity and selectivity of a monoclonal antibody against a given tumor cell-surface marker. Carcinoembryonic antigen (CEA) represents an attractive target in several cancers as it is highly expressed in breast cancer (BC) [9], medullary thyroid cancer (MTC) [10] and colorectal cancer [11]. Another use of iPET may be to exploit the specificity of its imaging to define the target tumor volume for SBRT. With the development of the linear accelerator combined with PET/CT, it is of major importance to study the impact of PET/CT imaging on the definition of SBRT volumes [12,13]

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