• DOI:10.1007/s12020-015-0661-3
• Corpus ID: 29295427

Visualization of tumor heterogeneity in neuroendocrine tumors by positron emission tomography

@article{Lapa2015VisualizationOT,
  title={Visualization of tumor heterogeneity in neuroendocrine tumors by positron emission tomography},
  author={Constantin Lapa and Rudolf A. Werner and Ken Herrmann},
  journal={Endocrine},
  year={2015},
  volume={51},
  pages={556-557}
}

• C. Lapa, R. Werner, K. Herrmann
• Published 1 March 2016
• Medicine, Biology
• Endocrine

A 50-year-old woman was diagnosed 15 months ago with a well-differentiated neuroendocrine tumor (NET) of the pancreatic tail (Ki-67: 10 %) and synchronous liver metastases. Consecutively, systemic treatment with octreotide was initiated. Due to progression, 2nd line treatment with peptide receptor radionuclide therapy (PRRT) using the Lu-labeled somatostatin analog DOTA-D-Phe1-Tyr3-octreotide (DOTATOC) was initiated. After three cycles of PRRT, somatostatin receptor (SSTR)-based positron emission tomography (PET) with Ga-labeled DOTATOC in combination with contrastenhanced computed tomography (CE-CT) was performed for restaging. In comparison to pre-therapeutic imaging, DOTATOC-PET demonstrated no significant change of both primary and known liver metastases highly expressing SSTR subtype II (Fig. 1, left). However, CE-CT revealed numerous significantly progressive, SSTR-negative intrahepatic lesions, highly suspicious for undifferentiated metastases. Accordingly, a PET/CT with the glucose analog [F]fluordeoxyglucose (FDG) was performed. FDGPET depicted increased focal uptake in all SSTR-negative lesions corroborating the CT findings (Fig. 1, right). Interestingly, almost all SSTR-positive lesions showed no or only weak FDG-accumulation (Fig. 1). The patient underwent CT-guided liver biopsy of an SSTR-negative, FDG-positive liver lesion confirming poorly differentiated metastasis of the known NET with a proliferative activity (Ki-67) of 15 %. Consequently, PRRT was stopped and patient management was changed to chemotherapy with streptozotocin and 5-fluorouracil. The patient underwent four treatment cycles. Recently, 12-months’ follow-up revealed stable disease. SSTR-PET/CT has been established as the standard imaging tool for well-differentiated NET due to a superior tumor detection rate compared to conventional receptor scintigraphy and multi-slice CT [1]. FDG-PET/ CT as a marker of increased glucose use of tumor cells has low sensitivity in well-differentiated NET. However, in advanced disease and intermediateand high-grade tumors, a mixture of welland poorly differentiated tumor lesions may be present. In aggressive NET with high proliferation rates, FDG-PET/CT remains the radiopharmaceutical of choice [2, 3]. Therefore, in conjunction with (multi-phase) CE-CT, functional imaging with both SSTRand FDG-PET may be performed for comprehensive tumor assessment, help to address different biological properties of NET, and to guide re-biopsies to de-differentiated tumor lesions in order to overcome histologic selection bias. In our case, the combination of SSTRand FDG-PET directly impacted on diagnostic work-up as well as patient management by revealing a multitude of vital, SSTR-negative liver metastases. Its value for therapeutic decision-making has been recently shown to be [50 % [4].