ReviewPET/CT with 68Gallium-DOTA-peptides in NET: An overview
Section snippets
68Ga-DOTA-TOC
68Ga-DOTA-TOC was the first tracer to be employed in NET imaging and was reported to present a high tumour to non-tumour contrast and a higher sensitivity compared to SRS [16], [17].
The study with the largest patients population (84 pts with NET), reported sensitivity (97%) for DOTA-TOC was superior to CT (61%) and SRS (52%) for the detection of NET lesions, especially in case of small tumours at nodal or bone level [18]. In particular, in a comparison study of 51 patients with well
68Ga-DOTA-NOC
68Ga-DOTA-NOC is also increasingly used in several centres: compared to DOTA-TOC, DOTA-NOC is able to bind with good affinity also to sst3 [13] and was reported to have a more favourable dosimetry [20]. The good sensitivity of 68Ga-DOTA-NOC was reported especially for small lesions, particularly at node and bone level [21], or in cases with an unusual anatomical localization [22].
68Ga-DOTA-NOC PET/CT was also reported to be more helpful than CT and SRS for the detection of unknown primary
68Ga-DOTA-TATE
68Ga-DOTA-TATE is characterized by a very high affinity for sst2 [13] with a considerably higher affinity than 111In-DTPAoctreotide [26].
In a recent paper, 51 patients (35 negative and 16 equivocal for uptake on SRS) were studied by 68Ga-DOTA-TATE PET. 68Ga-DOTA-TATE PET identified significantly more lesions than SRS and changed management in 36 patients (70.6%), who were subsequently deemed suitable for PRRT [27].
Comparison studies
A few studies in the literature compared the sensitivity of 68Ga-DOTA-peptides with metabolic tracers in NET patients, namely 18F-FDG and 18F-DOPA.
The only available study of direct comparison between 68Ga-DOTA-NOC and 18F-DOPA studied a limited patients population (13 pts): DOTA-NOC showed a higher number of lesions (71 vs. 45) and in more cases identified the site of the occult primary (6 vs. 2 of 8 non-operated cases) [28].
68Ga-DOTA-TATE was also compared with 18F-DOPA [29] and showed
PET/CT imaging protocol using 68GA-DOTA-peptides
PET/CT acquisition starts at 60 min after intravenous injection of approximately 100 MBq (75–250 MBq) of the radiolabeled peptide (such as 68Ga-DOTA-NOC, 68Ga-DOTA-TOC, etc.). The amount of injected radioactivity strictly depends on the daily production of the generator for each single elution (usually ranging between 300 and 700 MBq) and, of course, by the number of patients scanned per day.
Since sst are widely dispersed within the human body, different organs may be imaged by tracers binding to
Conclusions
The recent introduction of 68Ga-DOTA-peptides completely revolutioned the diagnostic approach to NET imaging with a direct impact on clinical management.
All described compounds (68Ga-DOTA-TOC, -NOC, -TATE) have been reported to be accurate for the localization of well differentiated NET lesions, performing better than CT and SRS.
PET assessment of NET with 68Ga-DOTA-peptides not only provides an accurate detection of even small-sized lesions, but also non-invasively provides valuable information
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