Jager P L, Meijer W G, Kema I P, Willemse P H, Piers D A, de Vries E G
Department of Nuclear Medicine, University Hospital Groningen, The Netherlands.
J Nucl Med. 2000 Nov;41(11):1793-800.
Carcinoid tumors can produce serotonin (5-hydroxytryptamine) and catecholamines from the precursors tryptophan and tyrosine. Our aim was to evaluate the tyrosine analog L-3-[123I]iodo-alpha-methyltyrosine (IMT) in the detection and the determination of biochemical activity of these tumors in comparison with 111In-labeled [diethylenetriaminepentaacetic acid (DTPA)-D-Phe1]-octreotide (111In-octreotide) scintigraphy.
SPECT and planar whole-body imaging were performed 15 min after administration of 300 MBq IMT in 22 patients with metastatic carcinoid tumors. The number of lesions detected was compared with the number detected by 111In-octreotide scintigraphy. The size and intensity of uptake of all lesions were graded using a simple scoring system, yielding a total body uptake score for both tracers. These scores were compared (nonparametric correlation) with biochemical markers of serotonin and catecholamine metabolism.
IMT SPECT detected only 63 of 145 lesions detected by 111In-octreotide imaging (43%). IMT SPECT performance was best in the liver (60% detection rate). Both IMT uptake and 111In-octreotide uptake scores correlated with markers of serotonin metabolism (respective values for urinary 5-hydroxyindoleacetic acid: r = 0.67 and 0.48, P < 0.001 and 0.05; for urinary serotonin: r = 0.56 and 0.40, P = 0.002 and 0.05; and for platelet serotonin: r = 0.57 and 0.45, P < 0.01 and 0.05). No correlation with adrenaline or noradrenaline metabolites was found. However, IMT uptake, but not 111In-octreotide uptake, correlated with dopamine metabolite excretion (homovanillic acid: r = 0.60, P < 0.05; and dopamine relative sum: r = 0.61, P < 0.05). IMT uptake was higher in patients with increased dopamine metabolite excretion (P = 0.05).
IMT uptake can be demonstrated in carcinoid lesions, but the method detected only 43% of carcinoid lesions that were positive on 111In-octreotide scintigraphy. Uptake of both tracers is related to the serotonin secretory activity. However, IMT uptake, but not 111In-octreotide uptake, was related to tumor dopamine metabolism. These findings may be of interest in the metabolic targeting of carcinoids.
类癌肿瘤可从前体物质色氨酸和酪氨酸生成血清素（5-羟色胺）和儿茶酚胺。我们的目的是评估酪氨酸类似物L-3-[123I]碘-α-甲基酪氨酸（IMT）在检测这些肿瘤以及确定其生化活性方面的效果，并与111In标记的[二乙烯三胺五乙酸（DTPA）-D-苯丙氨酸1]-奥曲肽（111In-奥曲肽）闪烁扫描法进行比较。
在22例转移性类癌肿瘤患者中，静脉注射300MBq IMT后15分钟进行单光子发射计算机断层扫描（SPECT）和全身平面显像。将检测到的病灶数量与111In-奥曲肽闪烁扫描法检测到的数量进行比较。使用简单评分系统对所有病灶的大小和摄取强度进行分级，得出两种示踪剂的全身摄取分数。将这些分数与血清素和儿茶酚胺代谢的生化标志物进行比较（非参数相关性分析）。
IMT SPECT仅检测到111In-奥曲肽显像所发现的145个病灶中的63个（43%）。IMT SPECT在肝脏中的表现最佳（检测率为60%）。IMT摄取分数和111In-奥曲肽摄取分数均与血清素代谢标志物相关（尿5-羟吲哚乙酸的相应值：r = 0.67和0.48，P < 0.001和0.05；尿血清素：r = 0.56和0.40，P = 0.002和0.05；血小板血清素：r = 0.57和0.45，P < 0.01和0.05）。未发现与肾上腺素或去甲肾上腺素代谢产物相关。然而，IMT摄取与多巴胺代谢产物排泄相关（高香草酸：r = 0.60，P < 0.05；多巴胺相对总和：r = 0.61，P < 0.05），而11In-奥曲肽摄取与多巴胺代谢产物排泄无相关性。多巴胺代谢产物排泄增加的患者IMT摄取更高（P = 0.05）。
类癌病灶中可显示IMT摄取，但该方法仅检测到111In-奥曲肽闪烁扫描法呈阳性的类癌病灶中的43%。两种示踪剂的摄取均与血清素分泌活性相关。然而，IMT摄取与肿瘤多巴胺代谢相关，而111In-奥曲肽摄取与肿瘤多巴胺代谢无关。这些发现可能对类癌的代谢靶向治疗具有重要意义。
