Neuroendocrine tumors (NET) are a network of rare tumors with common embryological origin.
Functional imaging plays a major role in the extension assessment and tumor characterization
of NETs. SPECT/CT with 111In-pentetreotide is the recommended test when tumors are well
differentiated (grade G1 or G2). It has a real interest in diagnosis, in therapeutic
decision-making (in particular by cold somatostatin analogues or in PRRT) and in the
systematic follow-up of patients. Nevertheless, SPECT/CT procedure makes for a relatively
long review. In addition, scintigraphy has a lower spatial resolution than PET technology and
remains of limited interest for signal quantification.
However, the ability to locate and quantitatively measure the absorption of
radiopharmaceuticals in the target tissues is a major challenge in oncology for the
characterization of the disease.
Recent developments in radiopharmacy have made it possible to target NETs in PET imaging
through the use of somatostatin analogues coupled with positron emitters, called 68Ga-DOTA
peptides. The diagnostic performance of 68Ga-DOTApeptide PET/CT appears to be superior to
SPECT/CT with 111In-pentetreotide. A marketing authorization has thus recently been issued in
France for the use of 68Ga-DOTATOC.
Historically, the recommended quantification method in PET was based on the instantaneous
measurement in static acquisition (3D) of the maximum of the standardized uptake value
(SUVmax). This approach has the disadvantage to measure the signal at a time "t" for a single
voxel of the image. Dynamic acquisition methods (4D) have been proposed to extract a
radiotracer absorption coefficient (Ki) for a lesion. Several studies have demonstrated the
superiority of Ki versus SUVmax in 18FDG PET/CT for the diagnostic management, therapeutic
evaluation and prognosis of various solid cancers.
However, no work has validated this approach in PET / CT at 68Ga-DOTATOC as part of the
prognostic evaluation of NETs.
The objective of the study is to evaluate the prognostic value of the tumor absorption
coefficient Ki resulting from a 4D whole-body dynamic acquisition in PET / CT at 68Ga-DOTATOC
in patients with well-differentiated NETs grade I or II according to the WHO classification