Comparison of 18F-DOPA Versus 68Ga-DOTATOC as Preferred PET Imaging Tracer in Well-Differentiated Neuroendocrine Neoplasms.

PURPOSE

The aim of this study was to retrospectively compare 18F-FDOPA versus 68Ga-DOTATOC PET in lesion detection rates and laboratory tumor markers in patients with neuroendocrine neoplasms (NENs).

PATIENTS AND METHODS

All patients with histologically proven NEN between May 2015 and February 2019 were included who underwent both 18F-DOPA and 68Ga-DOTATOC PET scans within 6 months from each other (mean, 75; median, 38; range, 2-168 days). All patients, except those with pancreatic NEN, received carbidopa before 18F-DOPA PET. Based on the number of lesions on both modalities, patients were divided into 3 categories: more lesions on 18F-DOPA (DOPA > DOTA), more lesions on 68Ga-DOTATOC (DOTA > DOPA), and equal number of lesions (DOPA = DOTA). Tumor markers chromogranin A, serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) within a maximum of 3 months around either scan were retrieved from the patients' charts.

RESULTS

18F-DOPA revealed significantly more lesions compared with 68Ga-DOTATOC (611 vs 385, P < 0.05). Twenty-four patients were included in the DOPA > DOTA group with 16 small intestinal (SI) NENs, 3 large intestinal, 4 pancreatic, and 1 tumor of unknown origin (TUO). For the 9 patients in the DOTA > DOPA group, 4 were SI, 2 pancreatic, 1 lung, and 2 TUOs. Twelve patients in the DOPA = DOTA group had 6 pancreatic tumors, 3 SI, 1 ovarian, and 2 TUOs. Only serotonin and 5-HIAA showed significant higher values for DOPA > DOTA compared with DOTA > DOPA (mean 24 vs 4, P < 0.05, and 320 vs 81, P < 0.05, respectively). Cutoff values of 20 nmol/109 for serotonin, 185 μg/L for chromogranin A, and 200 nmol/L for 5-HIAA were found to include almost exclusively DOPA > DOTA patients.

CONCLUSIONS

There is an advantage of carbidopa pretreated 18F-DOPA over 68Ga-DOTATOC PET, especially for large intestinal NENs with high levels of biomarkers. There seems to be a relationship between increased biomarker value and improved lesion detection rates with the 18F-DOPA PET scan, which requires further prospective analysis.