Henze Marcus, Mohammed Ashour, Schlemmer Heinz P, Herfarth Klaus K, Hoffner Simone, Haufe Sabine, Mier Walter, Eisenhut Michael, Debus Jürgen, Haberkorn Uwe
Department of Nuclear Medicine, University of Heidelberg, Heidelberg, Germany.
J Nucl Med. 2004 Apr;45(4):579-86.
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-[(123)I]iodo-alpha-methyl-L-tyrosine (IMT) and (99m)Tc(I)-hexakis(2-methoxyisobutylisonitrile) (MIBI) and the PET tracer (18)F-FDG.
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 (18)F-FDG PET and by (99m)Tc-MIBI and (123)I-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.
(123)I-IMT yielded the best ROC characteristics and was the most accurate for classification, with an area under the ROC curve (A(z)) of 0.991. The A(z) of (18)F-FDG (0.947) was not significantly lower than that of (123)I-IMT. The difference in the A(z) of (99m)Tc-MIBI (0.713) from the A(z) of the other tracers used in our study was highly significant (P </= 0.01). (99m)Tc-MIBI SPECT was of low accuracy and, especially, of poor sensitivity even at modest specificity values.
(123)I-IMT SPECT imaging of amino acid transport accurately detects tumor progression in patients with irradiated LGA. In contrast to (123)I-IMT, (18)F-FDG PET was slightly less accurate for classification, and (99m)Tc-MIBI SPECT was of limited value. Imaging of amino acid transport with (123)I-IMT is a valuable additional tool for the follow-up of LGA, allowing early, noninvasive differentiation of lesions with ambiguous morphology after irradiation.
肿瘤进展与放射性坏死的鉴别是肿瘤神经放射学中最困难的任务之一。肿瘤代谢的功能成像有助于完成这项任务，但示踪剂的选择仍存在争议。据我们所知，这项对接受放疗的低级别星形细胞瘤（LGA）进行随访的前瞻性研究，是首次对单光子发射计算机断层扫描（SPECT）示踪剂3-[(123)I]碘-α-甲基-L-酪氨酸（IMT）和(99m)Tc(I)-六甲基异丁基异腈（MIBI）以及正电子发射断层扫描（PET）示踪剂(18)F-氟代脱氧葡萄糖（FDG）的诊断性能进行个体内评估的受试者操作特征（ROC）分析。
我们对17例最初经组织学证实为LGA并接受立体定向放射治疗的患者进行了检查，这些患者在磁共振成像（MRI）上出现了新的钆双醋二胺增强病变（n = 26）。当时，MRI无法区分进展性肿瘤和非进展性肿瘤。在进行(18)F-FDG PET以及(99m)Tc-MIBI和(123)I-IMT SPECT检查后，紧接着进行了MRI检查。根据PET或SPECT后26.6±6.�个月的前瞻性随访（通过临床检查、MRI和质子磁共振波谱），将病变分为进展性肿瘤（n = 17）或非进展性肿瘤（n = 9）。
(123)I-IMT产生了最佳的ROC特征，分类准确性最高，ROC曲线下面积（A(z)）为0.991。(18)F-FDG的A(z)（0.947）并不显著低于(123)I-IMT的A(z)。(99m)Tc-MIBI的A(z)（0.713）与我们研究中使用的其他示踪剂的A(z)差异非常显著（P≤0.01）。(99m)Tc-MIBI SPECT准确性较低，尤其是即使在适度的特异性值下，敏感性也很差。
(123)I-IMT SPECT对氨基酸转运的成像能够准确检测接受放疗的LGA患者的肿瘤进展。与(123)I-IMT相比，(18)F-FDG PET分类准确性略低，(99m)Tc-MIBI SPECT价值有限。(123)I-IMT对氨基酸转运的成像对于LGA的随访是一种有价值的辅助工具，能够在放疗后对形态模糊的病变进行早期、非侵入性鉴别。
