Use of PET-CT with 11C-Methionine in the Primary Diagnosis of Gliomas

Objective. To study the accumulation of 11C-methionine in primary brain tumors of different types and intact brain tissue. Materials and methods. A total of 40 patients (21 men and 19 women) with gliomas with different levels of malignancy (Grade I–IV) were studied. All patients underwent PET-CT investigations with 11C-methionine and MRI scans with contrast enhancement. Standardized uptake values (SUV) were determined for tumors and intact tissue, along with the index of accumulation (IA) and tumor volume. Results. A large degree of individual variability was found in methionine uptake into unaffected brain tissue (SUV was 0.47–1.73 for the frontal lobe); metabolism of this amino acid was greater in women (SUV frontal lobe 1.05 ± 0.24 in men and 1.32 ± 0.22 in women). IA values gave better discrimination of gliomas in terms of the degree of anaplasia than SUV values; in particular, these were statistically significantly different for Grade III and Grade IV gliomas (2.64 ± 0.98 and 3.83 ± 0.75, p < 0.05). The lowest levels of methionine metabolism were noted in the subgroup with diffuse astrocytomas (IA = 1.52 ± 0.57), and this was lower than in anaplastic astrocytomas (IA = 2.34 ± 0.77, p < 0.05). Conclusions. Results obtained using PET-CT with 11C-methionine demonstrated high informativeness in the differential diagnosis of gliomas with low and high levels of malignancy (Grade I–II had IA = 1.66 ± 0.71 Grade III–IV had IA = 3.18 ± 1.06, p < 0.05) and in demarcating between diffuse astrocytomas with Grade II and III anaplasia. Furthermore, high individual variability was demonstrated in the parameter SUV in intact brain matter, along with differences in amino acid metabolism in different areas.