Indium-111 octreotide scintigraphy of Merkel cell carcinomas and their metastases

Background:Somatostatin receptor scintigraphy (SRS) may beof interest for staging Merkel Cell Carcinoma (MCC). This study wasundertaken to evaluate the sensitivity and specificity of SRS and todetermine its role compared to conventional investigations.Patients and methods:From 1993 to December 2000, 20patients (10 females and 10 males, aged from 38 to 88, mean 66 years)were included prospectively. At the time of SRS: 12 patients had beendiagnosed as having stage I disease, 6 stage II and 4 stage III. Twopatients had two SRS studies during the course of their disease. SRS wasperformed with Indium-111 pentetreotide (Octreoscan®), aradiolabelled somatostatin analogue. Patients were treated according tothe clinical stage. A regular follow-up was scheduled every threemonths.Results:SRS depicted stage I and II MCC tumour sites withan overall sensitivity of 78% (95% confidence interval(CI): 40%–97%) and a specificity of 96%(81%–100%). The histopathological diagnosis was usedas the gold standard. Sites visualised by SRS were compared to thosedetected with conventional modalities and to follow-up data for allstages: SRS visualised four out of five primary tumour sites, six out ofeight lymph node sites, no skin metastases (14 sites in 2 patients), twoout of three thoracic metastases and zero out of two hepatic metastases.SRS did not influence treatment decision-making in any of the cases.Conclusions:Although SRS seems highly specific in MCC andcould be of help in difficult cases, it cannot be recommended forroutine evaluation.