Prognostic Interest of a Whole Body Dynamic PET Acquisition in Pre-therapeutic 68Ga-DOTATOC PET/CT for Neuroendocrine Tumors

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