Prädiktion der pharmakologischen Wirkung von Octreotid bei Akromegalie mittels ¹¹¹In-Pentetreotid-Szintigraphie und Berechnung eines hypophysären Uptake-Index

Zusammenfassung

Ziel: Ziel unserer prospektiven Studie war die optimierte Bestimmung des hypophysären Somatostatin-Rezeptorstatus in der 111 -In-Pentetreotid-Szintigraphie und der intraindividuelle Vergleich mit dem pharmakologischen Effekt von Octreotid bei florider Akromegalie. Methoden: Bei n = 22 Patienten mit Wachstumshormon-(GH)-sezernierendem Hypophysenadenom wurde eine 111-In-Pentetreotid-Szintigraphie durchgeführt und die spezifische Nuklidakkumulation in der Hypophysenregion (Auswertung sowohl visuell als auch semiquantitativ mittels ROI-Technik und Berechnung verschiedener Uptake-Indizes) mit dem akuten GH-Abfall nach 100 ug Octreotid s.c. (Octreotid-Akuttest) korreliert. Ergebnisse: Der von uns vorgeschlagene Uptake-Index (Quotient zirkuläre Hypophysen-ROI : irreguläre Zerebrum-ROl, jeweils cts/pixel nach Untergrund-Korrektur im sagittalen SPECT-Schnitt mit der maximalen Hypophysendarstellung 24 h p. i.) korreliert am besten mit dem pharmakologischen Effekt (akuter GH-Abfall) von Octreotid; seine obere Normgrenze liegt im Bereich von 3,5. Schlußfolgerungen: Da sich häufig auch die normale Hypophyse szintigraphisch darstellen läßt, ist die rein visuelle Abgrenzung zum pathologischen Rezeptorstatus manchmal uneindeutig. Ein mittels standardisierter ROI-Technik berechneter, hypophysärer Uptake-Index erleichert diese Abgrenzung und hilft so, mögliche Responder für eine Octreotid-Langzeittherapie zu selektieren.

Summary

Aim: The aim of our prospective study was to optimize the determination of the pituitary somatostatin receptor status by means of 111-ln-pentetreotide scintigraphy and to compare it intraindividually with the pharmacological effect of octreotide in active acromegaly. Methods: In n = 22 patients with growth hormone (GH) secreting pituitary adenoma, 111-ln-pentetreotide scintigraphy was performed, and the specific radionuclide accumulation in the pituitary area (evaluation visually as well as semiquantitatively by means of ROI technique and calculation of various uptake indices) was correlated with the acute drop of GH after administration of 100 ug octreotide s.c. (octreotide acute test). Results: The uptake index we propose (cts/pixel-ratio circular pituitary ROI : irregular cerebrum ROI after background correction in the sagittal SPECT slice with maximum pituitary uptake 24 h p. i.) correlates best with the pharmacological effect (acute decrease of G H levels) of octreotide; its upper normal limit amounts to 3.5. Conclusion: As often the normal pituitary gland can be visualized scintigraphically, the purely visual differentiation between a normal and a pathological receptor status sometimes is equivocal. A pituitary uptake index, calculated by means of a standardized ROI technique, facilitates this discrimination and so contributes to select possible responders for a treatment with octreotide.

Schlüsselwörter

111 -In-Pentetreotid-Szintigraphie - Octreotid - Somatostatin-Rezeptoren - Hypophysenadenome - Akromegalie

Keywords

111-ln-pentetreotide scintigraphy - octreotide - somatostatin receptors - pituitary adenomas - acromegaly

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