Somatostatin receptor imaging is a valuable tool in the diagnosis, follow-up and treatment planning of neuroendocrine tumor (NET) patients. Positron emission tomography (PET) based tracers using (68)Ga as the radioisotope have in most centers replaced single-photon emission tomography (SPECT) based tracers as the gold standard. (64)Cu-DOTATATE is a new PET tracer that has been shown to be far superior compared to the SPECT tracer (111)In-DTPA-octreotide. Due to advantages of (64)Cu compared to (68)Ga, we hypothesize that the tracer could have a higher sensitivity than (68)Ga-based tracers. To test this hypothesis, we compared on a head-to-head basis the diagnostic performance of (64)Cu-DOTATATE with that of (68)Ga -DOTATOC in NET patients.

METHODS: Fifty-nine NET patients were scanned both with (64)Cu-DOTATATE and (68)Ga-DOTATOC PET and computed tomography (CT) and compared on a head-to-head basis. Discordant lesions were verified during at least 30 months of follow-up.

RESULTS: A total of 701 lesions were concordantly detected on both (64)Cu-DOTATATE and (68)Ga-DOTATOC PET/CT scans while an additional 68 lesions were found by only one of the scans. (64)Cu-DOTATATE showed 42 lesions not found on (68)Ga-DOTATOC of which 33 were found to be true positive on follow up. (68)Ga-DOTATOC showed 26 lesions not found on (64)Cu-DOTATATE of which 7 were found to be true positive on follow up. False positives were mainly lymph node lesions. Accordingly, 83% of the additional true lesions only found on one of the scans were found by (64)Cu-DOTATATE. On a patient-basis additional true lesions were found by (64)Cu-DOTATATE and (68)Ga-DOTATOC in 13 and 3 patients, respectively. All patients with additional lesions also had concordant lesions found by both scans.

CONCLUSION: (64)Cu-DOTATATE possesses advantages in the detection of lesions in NET patients compared to (68)Ga-DOTATOC. Although patient based sensitivity was the same for (64)Cu-DOTATATE and (68)Ga-DOTATOC in this cohort, significant more lesions were detected by (64)Cu-DOTATATE. Furthermore, the shelf life of more than 24 hours and the scan window of at least 3 hours make (64)Cu-DOTATATE very favorable and easy to use in the clinical setting.