Intraindividual comparison of 68Ga-DOTA-TATE and 18F-DOPA PET in patients with well-differentiated metastatic neuroendocrine tumours

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Abstract

Aim

To compare the diagnostic impact of 68Ga-DOTA-TATE and 18F-DOPA PET in the diagnosis of well-differentiated metastatic neuroendocrine tumours (NET).

Methods

PET/CT using both 68Ga-DOTA-TATE and 18F-DOPA was performed in 25 patients with histologically proven metastatic NET (nine gut, five pancreas, six lung, one paranasal sinus, four with unknown primary). Analyses of PET examinations were patient-based (pathological uptake: yes/no), and based on tumour regions (primary tumour if present and metastases of liver, lung, bones and lymph nodes). The results were compared with the results of contrast enhanced CT, and with plasma serotonin levels, which were available in 24 of the 25 patients.

Results

Patient-based sensitivities were 96% for 68Ga-DOTA-TATE PET and 56% for 18F-DOPA PET. 68Ga-DOTA-TATE PET delineated metastases in 54 of 55 positive metastatic tumour regions in contrast to 29 of 55 delineated by 18F-DOPA PET. Overall, 68Ga-DOTA-TATE was superior to 18F-DOPA in 13 patients (two patients showed fewer positive tumour regions with 18F-DOPA PET). The results were comparable in 12 patients. In 13 of 24 patients, plasma serotonin levels were elevated, and 11 of these 13 patients showed pathological uptake of 18F-DOPA. Of the 11 patients with normal levels of serotonin, 3 also showed positive 18F-DOPA uptake. In patients positive for 18F-DOPA uptake the maximum tumour SUVs were correlated with the levels of serotonin (r=0.66, p=0.01).

Conclusion

In this study 68Ga-DOTA-TATE PET proved clearly superior to 18F-DOPA PET for detection and staging of NET. 18F-DOPA uptake tended to be increased in those patients with elevated plasma serotonin. We conclude that 18F-DOPA PET should be employed in patients with NET with negative 68Ga-DOTA-TATE PET and elevated plasma serotonin.