In Vivo Succinate Detection After External Beam Radiation Therapy in SDHx- Paragangliomas

Evolution of Succinate Accumulation Detected in Vivo by Spectroscopic Magnetic Resonance Imaging (1H-SRM) After External Beam Radiation Therapy in SDHx-mutated Patients With Cervical Paragangliomas

Qualitative and quantitative biomarker of response to radiotherapy is needed in paragangliomas. We aim at assessing the added value of 1H-SRM for the evaluation of early response to EBR therapy in patients with cervical SDHx PGL.

Paragangliomas (PGL) are rare neuroendocrine tumors inherited in 40% of cases. SDHx genes (SDHA, SDHB, SDHC, SDHD), encoding the 4 subunits of the mitochondrial enzyme succinate dehydrogenase (SDH), are the most frequently involved.

Accumulation of succinate, the substrate for SDH, is a very specific biomarker for these mutations. Recently, we have demonstrated the feasability of detecting and quantifying succinate in tumors in vivo, by magnetic resonance spectroscopy (1H-SRM).

Patients carrying these mutations frequently develop cervical PGL for which the treatment of choice is external beam radiation therapy (EBR).

The objective of this project is to determine the feasibility of using 1H-SRM for the evaluation of early response to EBR therapy in patients with cervical SDHx PGL.

Inclusion Criteria:

• Age ≥ 18 years
• Signed informed consent
• Patient with cervical PGL with planning of treatment with EBR
• Patient with an SDHx mutation or unknown genetic status
• Patient affiliated to a social security scheme

Exclusion Criteria:

• Pregnant woman
• Contraindication to MRI (implantable device, etc.)
• Impossibility of lying down without movement for 45 minutes (hyperalgesic patient, claustrophobia, etc.)
• PPGL having previously been the subject of local (excluding surgery) or systemic treatment
• PPGL <1 cm longest axis
• Patient under guardianship or curatorship