Zuijdwijk Marc D, Vogel Wouter V, Corstens Frans H M, Oyen Wim J G
Department of Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
Nucl Med Commun. 2008 Jul;29(7):636-41. doi: 10.1097/MNM.0b013e3282f813e1.
In differentiated thyroid carcinoma, persistent plasma thyroglobulin (Tg) is a specific marker for persistent or recurrent disease after thyroidectomy and radioiodine ablation. When Tg remains elevated and no substrate can be found on whole-body radioiodine imaging (131I-WBS), or even when recurrent disease is suspected with normal Tg, conventional imaging (CI) is often insufficient. As fluorodeoxyglucose (FDG)-PET has proven to be an effective modality for detecting various types of cancer, the utility of FDG-PET was analysed and compared with CI in this retrospective study in patients with differentiated thyroid cancer.
After total thyroidectomy and radioiodine ablation, 68 FDG-PET scans were performed in 39 patients with elevated Tg levels or clinical suspicion of recurrent disease. At the time of FDG-PET, 54 131I-WBS (in 30 patients) were negative, 14 (in 11 patients) were equivocal. Tg was normal at the time of 14 scans (10 patients) and elevated in 54 (in 33 patients). FDG-PET results were compared with histology, 131I-WBS and CI and clinical follow-up. Sensitivity and specificity were evaluated in various subgroups.
Overall, there were 35 true-positive, two false-positive, 20 true-negative and three false-negative FDG-PET scans. In six of these cases (one true positive, five true negative) FDG-PET was repeated without intervention and in an additional eight FDG-PET scans no definite conformation of abnormal FDG-PET could be obtained, so these results were not used for statistical analysis. Sensitivity, specificity, PPV and NPV for the whole group were 92, 88, 94 and 83%, respectively. In 38 scans performed on 31 patients with elevated Tg levels, who were not known with recurrence, this was 84, 100, 100 and 75%, respectively. In 16 scans in 10 patients with known recurrence (all with elevated Tg), sensitivity and PPV were 100% without false-positive or false-negative results. When Tg was not detectable (14 scans in 10 patients), sensitivity, specificity, PPV and NPV were 100, 75, 60 and 100%, respectively. After 35 FDG-PET scans (51%), there was a change in patient management by avoiding ineffective 131I treatment, by guiding surgical reintervention, or avoiding futile surgery. One FP FDG-PET resulted in an unnecessary surgical procedure. In 33 cases, FDG-PET did not lead to a change in treatment policy, which retrospectively would have been beneficial in six cases.
FDG-PET affected patient management in patients with differentiated thyroid cancer and negative 131I-WBS, not only when Tg is elevated, but also when Tg is not detectable and therefore the use of FDG-PET as a diagnostic tool is justified in these patients.
在分化型甲状腺癌中，甲状腺切除及放射性碘消融术后，血浆甲状腺球蛋白（Tg）持续升高是疾病持续或复发的特异性标志物。当Tg持续升高且全身放射性碘显像（131I-WBS）未发现病灶，甚至在Tg正常但怀疑复发时，传统显像（CI）往往不足。由于氟代脱氧葡萄糖（FDG）-PET已被证明是检测各类癌症的有效手段，本回顾性研究分析了FDG-PET在分化型甲状腺癌患者中的应用，并与CI进行比较。
39例Tg水平升高或临床怀疑复发的患者在甲状腺全切及放射性碘消融术后接受了68次FDG-PET扫描。进行FDG-PET检查时，54次131I-WBS（30例患者）结果为阴性，14次（11例患者）结果不明确。14次扫描（10例患者）时Tg正常，54次（33例患者）时Tg升高。将FDG-PET结果与组织学、131I-WBS、CI及临床随访结果进行比较。在各亚组中评估敏感性和特异性。
总体而言，FDG-PET扫描有35例假阳性、2例假阴性、20真阴性和3真阳性。其中6例（1例假阳性，5例真阴性）未经干预重复进行了FDG-PET检查，另外8次FDG-PET扫描未获得异常FDG-PET的确切证实，因此这些结果未用于统计分析。全组的敏感性、特异性、阳性预测值和阴性预测值分别为92%、88%、94%和83%。对31例Tg水平升高且未知复发的患者进行的38次扫描中，上述指标分别为84%、100%、100%和75%。对10例已知复发（均为Tg升高）的患者进行的16次扫描中，敏感性和阳性预测值为100%，无假阳性或假阴性结果。当检测不到Tg时（10例患者的14次扫描），敏感性、特异性、阳性预测值和阴性预测值分别为100%、75%、60%和100%。35次（51%）FDG-PET扫描后，通过避免无效的131I治疗、指导手术再次干预或避免不必要的手术，改变了患者的治疗方案。1例假阳性FDG-PET导致了不必要的手术。33例中，FDG-PET未导致治疗策略改变，回顾性分析显示其中6例本可从中获益。
FDG-PET对分化型甲状腺癌且131I-WBS阴性的患者治疗方案有影响，不仅在Tg升高时，而且在检测不到Tg时，因此在这些患者中使用FDG-PET作为诊断工具是合理的。
