Clinical interpretation of residual uptake in 11C-methionine positron emission tomography after treatment of basal ganglia germ cell tumors: report of 3 cases

Abstract

<jats:p>Although <jats:sup>11</jats:sup>C-methionine (MET)-PET has been used to diagnose intracranial germ cell tumors (GCTs) arising in the basal ganglia, whether this imaging technique is useful in assessing treatment response and residual tumor is still unclear. The authors report 3 cases of basal ganglia GCTs in which the residual MET uptake at the end of treatment did not develop into a relapse, even without additional treatment. Case 1 is a 22-year-old man who had a second relapse of a left basal ganglia germinoma with diffuse dissemination on the walls of both of his lateral ventricles. MET-PET revealed high MET accumulation around tumors and their surroundings (maximum standardized uptake value [SUVmax] 3.3). After all treatments, MET-PET demonstrated mild tracer accumulation in both basal ganglia (SUVmax 2.2). Progression-free survival was 56 months from the second relapse without any further treatment. Case 2 is a 17-year-old boy with a left basal ganglia germinoma that showed increased MET uptake (SUVmax 4.2). After treatment, MET-PET revealed residual MET uptake (SUVmax 2.4) along the left posterior limb of the internal capsule. Progression-free survival was 52 months from the start of treatment. Case 3 is a 7-year-old boy with a left basal ganglia choriocarcinoma with increased tumor MET uptake (SUVmax 2.5). A minor enhanced mass remained on MRI after treatment with residual MET accumulation (SUVmax 1.4). Progression-free survival was 44 months. Treatment strategies based on MET uptake on PET should be carefully designed in patients with basal ganglia GCTs to avoid overtreatment and complications.</jats:p>

Value of C-11 methionine PET/CT in patients with intracranial germinoma

“…For these reasons, MET PET is considered useful for tumor localization, tumor contouring, and treatment planning. Previous studies and case reports in patients with IG using MET PET have mainly done research on basal ganglia germinomas and described that MET PET is useful for detection of basal ganglia germinoma without mass effects, differential diagnosis of patients with progressive hemiparesis and hemiatrophy on MRI, assessment of treatment response and residual tumor, monitoring for tumor recurrence, and locating a precise biopsy target [ 3 , 6 , 7 , 10 , 11 , 14 ]. In another previous study in IGs, it elucidated the characteristic MET and FDG PET findings of 10 IGs that develop in basal ganglia, pineal region, and suprasellar region [ 9 ].…”

“…In a previous study on the distribution of MET in mouse malignant tumor models, MET uptake was mainly by viable cancer cells, and MET uptake by macrophages and granulation tissues was low [ 13 ]. Previous studies and case reports in patients with IG using MET PET have mainly done research on basal ganglia germinomas [ 3 , 6 , 7 , 10 , 11 , 14 ], and described that MET PET is useful for early detection of basal ganglia germinoma without overt mass formation, assessment of treatment response and residual tumor, and monitoring for tumor recurrence [ 3 , 6 , 7 , 10 ]. In previous studies, patients with basal ganglia germinoma presented only with hemiatrophy without any obvious mass formation on MRI, and the studies explained that MET PET was valuable for detecting the precise location of the tumor [ 10 , 11 ].…”

18F-FDG PET/CT Demonstrating Crossed Cerebellar Diaschisis Due to Germ Cell Tumor of the Basal Ganglia

“…9 Furthermore, PET/CT with 11 C-methionine has demonstrated its high diagnostic value for the assessment of disease, given its excellent contrast from the background and can therefore be useful also to guide biopsy and monitor treatment efficacy. 6,[8][9][10][11][12] Crossed cerebellar diaschisis refers to a depression in metabolism of a cerebellar hemisphere as a result of contralateral supratentorial lesions (infarcts, tumors, epileptic foci), arising from a disruption of corticopontocerebellar fibers across the thalamus. [13][14][15][16] This condition can be evaluated with PET/CT imaging, in particular with metabolic tracers ( 18 F-FDG) or perfusion tracers ( 15 O).…”

“…It is thought that cortical reduction of uptake is due to the progression of functional and metabolic decline that parallels the clinical symptoms 9 . Furthermore, PET/CT with 11 C-methionine has demonstrated its high diagnostic value for the assessment of disease, given its excellent contrast from the background and can therefore be useful also to guide biopsy and monitor treatment efficacy 6,8–12 . Crossed cerebellar diaschisis refers to a depression in metabolism of a cerebellar hemisphere as a result of contralateral supratentorial lesions (infarcts, tumors, epileptic foci), arising from a disruption of corticopontocerebellar fibers across the thalamus 13–16 .…”