Incremental Value of Delayed [68Ga]Ga-DOTATATE PET/MR in the Detection of Liver Metastases from Gastroenteropancreatic Neuroendocrine Tumors

Background: [ ⁶⁸ Ga]Ga-DOTATATE PET/CT has been widely used in the diagnosis and staging of gastroenteropancreatic neuroendocrine tumors (GEP-NETs), while PET/MR may have greater advantages in the diagnosis of hepatic lesions. This study aimed to compare the diagnostic performance of conventional [ ⁶⁸ Ga]Ga-DOTATATE PET/CT and delayed PET/MR in detecting hepatic metastases in patients with GEP-NETs. Methods: This prospective observational study enrolled GEP-NETs patients with liver metastases who underwent conventional [⁶⁸Ga]Ga-DOTATATE PET/CT followed by delayed PET/MR of the upper abdomen on the same day. Contrast-enhanced MRI served as the reference standard. Lesion detection rates, maximum standardized uptake value (SUVmax), target-to-background ratio (TBR), sensitivity, specificity, and accuracy were compared between the two modalities. Results: 46 patients (mean age 56.4±12.9 years, 18 males and 28 females) were included. A total of 542 liver metastases were identified, with PET/CT detecting 368 (67.9%) lesions and delayed PET/MR contributing an additional 146 (94.8%) lesions. For matched lesions, SUVmax and TBR values showed no statistically significant differences between PET/CT and delayed PET/MR imaging (17.2 ± 11.0 vs. 16.4 ± 10.8, P = 0.746; 4.1 ± 3.6 vs. 4.0 ± 2.8, P = 0.178, respectively). For additional lesions detected on delayed PET/MR, 54 high‑uptake liver metastases were identified (mean diameter 4.7 ± 1.9 mm; SUVmax 9.1 ± 2.2), along with 92 non‑uptake lesions (mean diameter 5.5 ± 2.3 mm; Z = –2.149, P  = 0.0315). The sensitivity, specificity and accuracy between conventional PET/CT and delayed PET/MR were (65.9% vs. 92.4%, P <0.001), (59.3% vs. 51.9%, P =0.77) and (65.6% vs.90.5%, P <0.001), respectively. Conclusion: Delayed PET/MR exhibits superior efficacy in detecting liver metastases compared to conventional PET/CT. The combined strategy of [ ⁶⁸ Ga]Ga-DOTATATE PET/CT and delayed PET/MR provides a more sensitive and precise approach for detecting liver metastases in patients with GEP-NETs.