Retrospektive Analyse der Ergebnisse präoperativer Lokalisationsdiagnostik von Nebenschilddrüsenadenomen mittels planarer 99mTechnetium-Sestamibi-Szintigraphie, SPECT und Sonographie beim primären Hyperparathyreoidismus in Abhängigkeit von Schilddrüsengröße und Schilddrüsenknoten

Left untreated, primary hyperparathyroidism (pHPT) is a disease with potentially serious consequences. Surgical excision of the diseased parathyroid tissue is currently the only established curative therapy. There are several different surgical techniques, ranging from minimally invasive surgery to bilateral cervical exploration. Preoperative localization is especially required when a minimally invasive technique is considered or in cases of recurrent disease. Several localization techniques exist but parathyroid scintigraphy and ultrasound are the most important. Reports in the literature suggest decreased sensitivity of both scintigraphy and cervical ultrasound in the case of multinodular goiter. The present study evaluates the sensitivity of Sestamibi scanning and cervical ultrasound to localize parathyroid adenoma in patients with pHPT, especially in patients with thyroid nodules or goiter. 55 Patients with pHPT were included in this retrospective clinical trial. All patients underwent planar 99m Technetium(Tc)-Sestamibi-dual-phase-scintigraphy at the University Hospital Marburg (Department of Nuclear Medicine) in 2001. Imaging consisted of 99mTc-Sestamibi-dual-phase-scintigraphy with planar scans from the neck and thorax acquired at 5, 15 and 120 minutes after the intravenous injection of 500-700 mega-Becquerel 99mTc-Sestamibi. 35 patients also underwent “single photon emission computed tomography” (SPECT) imaging for 3-D localization 240 minutes after an i.v. injection of 99mTc-Sestamibi. Following scintigraphy, all 55 patients underwent cervical ultrasound. The scintigraphy findings were known at the time the ultrasound was performed. Finally, all patients underwent surgery with a histological examination of the excised material to confirm the presence of one or more parathyroid adenomas (gold standard). Planar scintigraphy had a sensitivity of 46,7 %. SPECT imaging did not identify additional adenomas. Ultrasound had a sensitivity of 42,6 %. Clearly, ultrasound findings were influenced by the results of scintigraphy. Our data did not show decreased sensitivity in the presence of multinodular goiter. In contrast we found better sensitivity (48,1 %) if the volume of the thyroid gland was above the standard value. The presence of thyroid nodules did not increase the rate of false positive findings. However, it did increase the rate of false negative findings. This could perhaps be as a result of mistaking parathyroid adenomas for thyroid nodules, but this should have been detected in the ultrasound. Our reported sensitivities for both scintigraphy and ultrasound (46,7 % and 42,6 % respectively) are at the lower end of the range reported by other authors. One reason for this might be publication bias. Some clinical trials have very low patient figures. Likewise, some trials evaluate the ability to identify the correct side, as opposed to exact localization. This increases the sensitivity of a procedure by 10 to 20 %. In our study, this would have raised the sensitivity of scintigraphy by approximately 15 % and the sensitivity of ultrasound by approximately 13 %. Similarly, some trials were based on expert re-interpretation of the scans instead of the original interpretations. The most important methodological limitation of this study and a further explanation for the relatively low sensitivities, that were found, is the fact that an unknown number of patients, who for example had another conclusive preoperative diagnostic procedure, had an operation without having a scintigraphy preoperatively. This would indicate that preselected patients were included in this study. In conclusion we consider a prospective trial to be necessary.