Superior value of [18F]6-FDOPA PET/CT in staging of neuroendocrine tumors

Objectives [18F]6-fluoro-L-DOPA positron emission tomography(F-DOPA PET)has emerged as a sensitive and specific modality for staging and restaging patients with known or suspected carcinoid tumors,mainly in Europe.This study aimed to prospectively study the performance of FDOPA PET/CT in a Canadian cohort,compared to CT and somatostatin receptor scintigraphy(SRS).

Methods Required permissions for radiochemical manufacturing and clinical study protocols were obtained from Health Canada.Fluorine-18 labelled 6-FDOPA was synthesized based on direct fluorination of DOPA in HF/BF3.Whole body PET/CT was performed after injection of ~200 MBq[18F]6-FDOPA(Specific activity 200 ± 100 GBq/mmol)in patients with documented or suspected carcinoid tumors.All available data,including pathology/cytology,imaging tests and follow up data served as a composite reference standard.CT scanning and somatostatin receptor scintigraphy (SRS) was performed within a short interval using standard methods. We determined and compared diagnostic sensitivity and specificity using patient-based, region-based and lesion-based analysis for all 3 modalities. Image interpretation of PET was blinded from other studies.

Results Twenty three patients(M:F=13:10,age 34-82)with either a documented neuroendocrine tumor(n=18)or a suspicion for such a tumor based on clinical,imaging and biochemical data(n=5),were studied. 18F-DOPA PET/CT was positive in 18 of 18 patients with documented disease. Regional sensitivity/specificity was 94%/94% for PET, 63%/92% for CT, 59%/89% for SRS. Lesion based sensitivity was 98, 69, 44% for PET, CT and SRS, respectively. In the 5 patients with suspected recurrence CT localized disease in 1 patient, whereas all other modalities including PET were negative. In 6/23 patients PET results impacted directly on clinical management.

Conclusions FDOPA PET/CT had superior sensitivity to CT and SRS for detection of neuroendocrine tumors and metastases with a significant impact on clinical management