Head-to-Head Comparison of 18F-DOPA PET/CT and 68Ga-DOTANOC PET/CT in Patients With Midgut Neuroendocrine Tumors

Abstract

Purpose: The aim of this study was to compare retrospectively 18F-DOPA PET/CT versus 68Ga-DOTANOC PET/CT in a group of patients affected by midgut NET.

Patients and methods: Patients with histologically proven grade 1 or grade 2 midgut NET were explored after injection of 150 MBq of 68Ga-DOTANOC and 210 MBq of 18F-DOPA. The PET/CTs were analyzed visually and semiquantitatively at the patient level, regional level (7 defined regions), and lesion level (maximum of 5 lesions/organ). The criterion standard was determined on the basis of histology and imaging follow-up.

Results: Thirty patients (17 males and 13 females; median age, 63.5 years [37-82 years]) were included. Both PET/CTs were negative in 3 patients and positive in 25 patients. PET/CTs were discordant in 2 patients, with 18F-DOPA positive and 68Ga-DOTANOC negative. 18F-DOPA PET/CT detected more involved regions and more metastatic lesions than 68Ga-DOTANOC PET/CT in 6 (20%) and 10 (33.3%) patients, respectively. Of the 81 confirmed affected regions, 77 (95%) were detected by 18F-DOPA PET/CT and 71 (87.7%) by 68Ga-DOTANOC PET/CT (P < 0.0001). 18F-DOPA PET/CT detected significantly more lesions (211/221) than 68Ga-DOTANOC PET/CT (195/221), corresponding to a sensitivity of 95.5% and 88.2%, respectively (P < 0.0001). Tumor-to-background ratios were more favorable in liver for 18F-DOPA than for 68Ga-DOTANOC. Interestingly, a correlation was found between 18F-DOPA SUVmax and tumor burden and especially with the number of regions involved by the disease (P = 0.019).

Conclusions: 18F-DOPA PET/CT is superior to 68Ga-DOTANOC PET/CT for the detection of lesions, and when available, this tracer may be recommended as the first-line examination for an accurate staging of midgut NET.