PURPOSE: The aim of this study was to retrospectively compare F-FDOPA versus Ga-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 F-DOPA and Ga-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 F-DOPA PET. Based on the number of lesions on both modalities, patients were divided into 3 categories: more lesions on F-DOPA (DOPA > DOTA), more lesions on Ga-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: F-DOPA revealed significantly more lesions compared with Ga-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/10 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 F-DOPA over Ga-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 F-DOPA PET scan, which requires further prospective analysis.