CarciNor is working to raise the awareness for NET cancer, and we support and promote NET cancer research through CarciNor Research Fund. For 2015 the award was divided equally between Espen Thiis-Evensen (see English summary posted on December 9 2015), and Henning Langen Stokmo (who was awarded at the very end of 2015). For our international followers, we bring you the English protocol of the research project.
Association between Ki-67 proliferation index and maximum standard uptake value (SUVmax) on 18F-FDG-PET in advanced WHO G3 gastroenteropancreatic neuroendocrine carcinomas (GEP-NECs).
The main purpose is to demonstrate a correlation between the proliferation marker Ki-67 (number of cells in division, expressed in percent) by histopathological examination, and the FDG-intensity (SUV value) by 18F-FDG-PET imaging for WHO G3 GEP-NECs.
Positron emission tomography (PET) is a nuclear medicine imaging method based on metabolism- or molecular (and functional) imaging, in contrast to CT and MRI visualizing mostly anatomy or structures. PET uses a tracer labeled with a radioactive isotope which is injected intravenously into the patient and then imaged with a PET-camera. Both the tracer and isotope may vary, but the most common tracer is FDG (fluorodeoxyglucose), which is a sugar analog. The principle is that the more sugar the malignant cell uses, the more aggressive it is, and thus the higher FDG-intensity the malignancy has. We can measure this FDG-intensity with the PET-camera and (semi)quantify it with a variable called SUVmax.
Ki-67 is a cell marker of proliferation. It is used to estimate the growth rate of a given population of cells e.g. cancer cells, and is expressed as a percentage. This marker has a prognostic value for NETs and forms the basis for the current WHO-classification of NETs. The higher Ki-67, the more aggressive the cancer.
NECs generally have a higher FDG-intensity with 18F-FDG-PET than neuroendocrine tumours (NETs). 18F-FDG-PET may therefore be a very good way to map the entire disease burden and its biology (sugar metabolism) within the different lesions, without collecting tissue samples of all lesions to estimate the correct Ki-67. This would thus help to ensure correct grading (staging) of a NET. We know that the primary tumor and metastases tend to have different numbers of cells in division, and thus a different Ki-67. If a tissue sample is taken from a metastasis with a low Ki-67, you run a risk of incorrectly classifying the tumour. This has consequences for both prognosis and treatment, and further monitoring of the patient.
From a former- and another currently ongoing Nordic NEC-study, we wish to select those patients who have completed a 18F-FDG-PET study, to analyze the SUVmax of the primary tumor / metastases, and see whether this correlates with the Ki-67 of the histopathological specimens.
Text: Henning Langen Stokmo, Junior Consultant Physician in Nuclear Medicine, Radiology Resident at Oslo University Hospital
Photo: Oslo University Hospital, Ullevål