TY - JOUR T1 - PET and SPECT for Detection of Tumor Progression in Irradiated Low-Grade Astrocytoma: A Receiver-Operating-Characteristic Analysis JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 579 LP - 586 VL - 45 IS - 4 AU - Marcus Henze AU - Ashour Mohammed AU - Heinz P. Schlemmer AU - Klaus K. Herfarth AU - Simone Hoffner AU - Sabine Haufe AU - Walter Mier AU - Michael Eisenhut AU - Jürgen Debus AU - Uwe Haberkorn Y1 - 2004/04/01 UR - http://jnm.snmjournals.org/content/45/4/579.abstract N2 - Differentiation between tumor progression and radiation necrosis is one of the most difficult tasks in oncologic neuroradiology. Functional imaging of tumor metabolism can help with this task, but the choice of tracer is still controversial. This prospective study following up irradiated low-grade astrocytoma (LGA) was, to our knowledge, the first receiver-operating-characteristic (ROC) analysis that intraindividually evaluated the diagnostic performance of the SPECT tracers 3-[123I]iodo-α-methyl-L-tyrosine (IMT) and 99mTc(I)-hexakis(2-methoxyisobutylisonitrile) (MIBI) and the PET tracer 18F-FDG. Methods: We examined 17 patients, initially with histologically proven LGA and treated by stereotactic radiotherapy, who presented with new gadolinium-diethylenetriaminepentaacetic acid–enhancing lesions (n = 26) on MRI. At that time, MRI could not differentiate between progressive tumor and nonprogressive tumor. This MRI examination was closely followed by 18F-FDG PET and by 99mTc-MIBI and 123I-IMT SPECT. Lesions were classified as progressive tumor (n = 17) or nonprogressive tumor (n = 9) on the basis of prospective follow-up (through clinical examination, MRI, and proton MR spectroscopy) for 26.6 ± 6.6 mo after PET or SPECT. Results: 123I-IMT yielded the best ROC characteristics and was the most accurate for classification, with an area under the ROC curve (Az) of 0.991. The Az of 18F-FDG (0.947) was not significantly lower than that of 123I-IMT. The difference in the Az of 99mTc-MIBI (0.713) from the Az of the other tracers used in our study was highly significant (P ≤ 0.01). 99mTc-MIBI SPECT was of low accuracy and, especially, of poor sensitivity even at modest specificity values. Conclusion: 123I-IMT SPECT imaging of amino acid transport accurately detects tumor progression in patients with irradiated LGA. In contrast to 123I-IMT, 18F-FDG PET was slightly less accurate for classification, and 99mTc-MIBI SPECT was of limited value. Imaging of amino acid transport with 123I-IMT is a valuable additional tool for the follow-up of LGA, allowing early, noninvasive differentiation of lesions with ambiguous morphology after irradiation. ER -