A high ¹⁸F-FDOPA uptake is associated with a slow growth rate in diffuse Grade II-III gliomas

In diffuse Grade II-III gliomas, a high 3,4-dihydroxy-6-(¹⁸F)-fluoro-L-phenylalanine (¹⁸F-FDOPA) positron emission tomography (PET) uptake, with a standardized uptake value (SUV_max)/contralateral brain tissue ratio greater than 1.8, was previously found to be consistently associated with the presence of an isocitrate dehydrogenase (IDH) mutation, whereas this mutation is typically associated with a better prognosis. This pilot study was aimed to ascertain the prognostic value of this high ¹⁸F-FDOPA uptake in diffuse Grade II-III gliomas with regard to the velocity of diameter expansion (VDE), which represents an established landmark of better prognosis when below 4 mm per year.

20 patients (42 ± 10 years, 10 female) with newly-diagnosed diffuse Grade II-III gliomas (17 with IDH mutation) were retrospectively included. All had a ¹⁸F-FDOPA PET, quantified with SUV_max ratio, along with a serial MRI enabling VDE determination.

SUV_max ratio was above 1.8 in 5 patients (25%) all of whom had a VDE <4 mm/year (100%) and IDH mutation (100%). Moreover, a SUV_max ratio above 1.8 was associated with higher rates of VDE <4 mm/year in the overall population (45 vs 0%, p = 0.04) and also in the subgroup of patients with IDH mutation (45 vs 0%, p = 0.10).

This pilot study shows that in diffuse Grade II-III gliomas, a high ¹⁸F-FDOPA uptake would be predictive of low tumour growth, with a different prognostic significance than IDH mutation. Advances in knowledge: ¹⁸F-FDOPA PET in a single session imaging could have prognostic value in initial diagnosis of diffuse Grade II-III gliomas.