Contribution of Cerebral 18F-DOPA PET-CT Scan in High-grade Recurrent Gliomas

The use of contrast enhancement in enhancing -T1 MRI, due to the rupture of the blood-brain barrier may underestimate the volume to be irradiated. The natural course of these gliomas after first irradiation is a second relapse within 12 months with, in 40% of cases, relapses outside the initial radiation field.

Amino acid PET-CT (Positon Emission Tomography with Computed Tomography) could be an interesting alternative to tumor delineation because its results, do not depend on the rupture of the blood-brain barrier. Several studies have used amino acid PET in the planning of radiotherapy treatment for high-grade gliomas, but without a well-conducted prospective study. In the recurrent high-grade glioma population, no studies have been performed with 18F-DOPA.( 6-fluoro-[18F]-L-dihydroxyphenylalanine) The question therefore relates to the interest of cerebral 18F-DOPA PET-CT to improve the delineation of the volumes to be re-irradiated, during the recurrence of high-grade gliomas, and on the optimal methodology for determining GTV- PET.

To compare GTV-TEP and GTV-MRI volumes with each other, and the r-GTV, volume corresponding to the relapse objectified on the follow-up MRI, the analysis will be based on 3 parameters:

• DICE index, similarity index between 2 volumes,
• Contoured Common Volume (VCC), intersection of 2 volumes between them,
• Additional Contoured Volume (VSC), total volume delineated with imaging minus the common volume between 2 imageries.

Thus, within the rGTV relapse volume, it's important to know whether VSC of 18F-DOPA PET-CT is significant compared to that of MRI and would thus allow better definition of the volumes to be irradiated.

Inclusion criteria

• Adult > 18 and < 75 years old
• Status WHO ≤ 2
• Histological diagnosis of WHO grade III or IV glioma, in local recurrence after radiochemotherapy (60Gy/30 sessions + concomitant TEMOZOLOMIDE), postoperatively or exclusively.
• Recurrence in the field of initial radiotherapy
• Indication for stereotactic radiotherapy alone, validated in neuro-oncology CPR.
• Patient affiliated to a social security system
• Patient able to give consent

Exclusion criteria

• Contraindication to new radiotherapy
• First treatment other than standard radiochemotherapy (60Gy/30 session + concomitant TEMOZOLOMIDE), postoperative or exclusive.
• Contraindication to MRI and/or gadolinium injection
• Pregnancy, breastfeeding
• Follow-up of the patient impossible
• Persons deprived of liberty or under guardianship