Table 1.
Diagnostic Value of Different Amino Acid Tracers Compared to MRI
| MET | FET | FDOPA | |
|---|---|---|---|
| Value of amino acid PET for radiotherapy target delineation | BTV larger than contrast enhancement in WHO grade III/IV gliomas, validation of imaging findings by histology18,31 | BTV larger than contrast enhancement in WHO grade III/IV gliomas, validation of imaging findings by histology19,22,23,40,41 | Preliminary studies suggest that BTV larger than contrast enhancement in WHO grade III/IV gliomas20,45 |
| FET seems to be comparable to MET39 | FDOPA seems to be comparable to MET and FET46,47 | ||
| Amino acid PET-based radiotherapy (“dose painting”) in patients with newly diagnosed glioma | Radiation dose escalation to metabolically hyperactive foci in newly diagnosed glioblastoma patients is feasible and safe, with a median OS of 20 months29,59,60 | FET PET-based radiotherapy in newly diagnosed glioblastoma is safe, but OS could not be prolonged56 | FDOPA PET-based radiotherapy in WHO grade III/IV gliomas is safe57 a larger FDOPA PET study for tumor targeting with dose-escalated radiotherapy in newly diagnosed glioblastoma is ongoing58 |
| Amino acid PET-based re-irradiation (“dose painting”) in patients with relapsed glioma | MET PET-based re-irradiation may lead to improved OS compared with radiotherapy planning based on conventional MRI67 | A prospective multicenter phase II trial is ongoing70 | n.a. |
| Use of amino acid PET for assessment of response to radiotherapy | In contrast to conventional MRI, MET PET parameter reduction post-radiotherapy was significantly associated with a longer PFS80,81 | Superior to conventional MRI; metabolic response to temozolomide chemoradiation predictive for OS77,78 | n.a. |
| Differentiation of glioma progression from radiation-induced changes | Higher accuracy than conventional MRI,93,103 but seems to be lower in comparison to FET103 | Higher accuracy than conventional MRI66,84,95–99 dynamic FET PET acquisition may further increase diagnostic accuracy95,98,99 | Higher accuracy than conventional MRI94,100–102 |
Abbreviations: BTV, biological tumor volume; FDOPA, 3,4-dihydroxy-6-[18F]-fluoro-l-phenylalanine; FET, O-(2-[18F]-fluoroethyl)-l-tyrosine; MET, [11C-methyl]-l-methionine; OS, overall survival; PFS, progression-free survival.