Performances of 18F-FDOPA PET/CT in the Preoperative Evaluation of the Peritoneal Cancer Index in Small Intestine Neuroendocrine Tumors.

PURPOSE: Peritoneal carcinomatosis (PC) concerns up to 30% of patients with a neuroendocrine tumor (NET), especially of the small intestine. Aggressive management of carcinomatosis seems to be justified, especially with regard to possible mechanical complications. 18F-FDOPA PET/CT is known to be the most sensitive imaging modality for the detection of small bowel NET metastases, yet its performance in the detection of PC is not well studied. The main objective of our study is to evaluate the performances of preoperative 18F-FDOPA PET/CT in the prediction of surgical peritoneal cancer index. METHODS: All patients referred to our center for an 18F-FDOPA PET/CT from October 2017 to January 2021 were retrospectively screened. Images were analyzed by a blinded nuclear medicine physician, and peritoneal abnormalities were reported to comply with the surgical peritoneal cancer index standard. Per patient analysis and per region analysis were then conducted. RESULTS: Thirty-three patients were included; 6 patients (35 regions) presented a peritoneal carcinosis. Peritoneal Carcinomatosis Index (PCI) estimated on 18F-FDOPA PET/CT was significantly and strongly correlated to surgical PCI (r = 0.96, P < 0.001). Patient-based sensitivity, specificity, negative predictive value, and positive predictive value for 18F-FDOPA PET/CT were 100%, 93%, 100%, and 75%, respectively. The agreement between 18F-FDOPA and surgery regarding PC was excellent (Cohen κ = 0.82 on per patient analysis, 0.74 on per region analysis). CONCLUSIONS: A preoperative estimation of PCI is achievable based on 18F-FDOPA PET/CT for small intestine NET and could allow to optimize surgical procedures and patient selection.

Multimodality Imaging Features of a Misleading Sacral Giant Cell Tumor in 18F-FDG PET/CT, Bone Scan, and MRI.

We report the case of an asymptomatic 66-year-old woman referred for initial staging of an invasive ductal breast carcinoma. Initial workup incidentally revealed a bone tumor of right sacral wing corresponding to a giant cell tumor (GCT). We present the imaging characteristics of GCT on Tc-HDP bone scan (doughnut sign), F-FDG PET/CT (intense and heterogeneous uptake of a prominent geographic lytic lesion with partial rupture of cortical), and MRI (hyposignal with gadolinium enhancement on T1-weighted images and heterogeneous hypersignal on T2-weighted images). GCT is a benign but locally aggressive primary bone tumor, constituting a pitfall and diagnostic challenge.

Hepatic Metastases From Prostatic Adenocarcinoma Without Elevated 18F-Choline Activity.

We report the case of a 69-year-old man referred for F-fluorocholine (FCH) PET/CT for a biochemical recurrence of prostate cancer. FCH PET/CT demonstrated 2 hypodense hepatic lesions with no uptake but progressing in size compared with a previous assessment. MRI showed a suspicious peripheral contrast enhancement, raising the question of a liver metastasis. Histopathologic examination concluded to a prostate adenocarcinoma metastasis. This case highlights an unusual pitfall in FCH PET/CT: the lack of uptake in prostatic liver metastasis is presumably due to the partial volume effect induced by the necrotic center and the high uptake of the liver.