Estimated Fetal Radiation Dose From 18 F-FDG PET/CT During the Second and Third Trimesters of Pregnancy.

PURPOSE: Data published in the literature concerning the doses received by fetuses exposed to a 18 F-FDG PET are reassuring but were obtained from small and heterogeneous cohorts, and very few data are available concerning the fetal dose received after exposure to both PET and CT. The present study aimed to estimate the fetal dose received following a PET/CT exposure using methods that include anthropomorphic phantoms of pregnant women applied on a large cohort. PATIENTS AND METHODS: This retrospective multicenter study included 18 pregnant patients in the second and third trimesters. For PET exposure, the fetal volume and mean concentration of radioactivity in the fetus were measured by manually drawing regions of interest. Those data, combined with the time-integrated activities of the fetus and the mother's organs, were entered into the OLINDA/EXM software 2.0 to assess the fetal dose due to PET exposure. To estimate the fetal dose received due to CT exposure, 2 softwares were used: CT-Expo (based on geometric phantom models of nonpregnant patients) and VirtualDose (using pregnant patient phantoms). RESULTS: The fetal dose exposure for PET/CT examination in the second trimester ranged from 5.7 to 15.8 mGy using CT-Expo (mean, 11.6 mGy) and from 5.1 to 11.6 mGy using VirtualDose (mean, 8.6 mGy). In the third trimester, it ranged from 7.9 to 16.6 mGy using CT-Expo (mean, 10.7 mGy) and from 6.1 to 10.7 mGy using VirtualDose (mean, 7.6 mGy). CONCLUSIONS: The estimated fetal doses were in the same range of those previously published and are well below the threshold for deterministic effects. Pregnancy does not constitute an absolute contraindication for a clinically justified hybrid 18 F-FDG PET/CT.

Outcome on Mesenteric Mass Response of Small-Intestinal Neuroendocrine Tumors Treated by 177Lu-DOTATATE Peptide Receptor Radionuclide Therapy: The MesenLuth Study, a National Study from the French Group of Endocrine Tumors and Endocan-RENATEN Network.

A mesenteric mass (MM), characterized by fibrotic reaction, is present in most small-intestinal neuroendocrine tumors (SI-NETs). 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) has shown its efficacy in patients with progressive SI-NETs. However, because of specific tissue characteristics of desmoplastic MMs, we hypothesize that these lesions may be refractory to 177Lu-DOTATATE PRRT. Methods: From the national French Groupe d'étude des Tumeurs Endocrines database, we identified patients with an advanced SI-NET and a MM (≥2 cm with a retractile aspect) of a SI-NET treated by at least 1 course of 177Lu-DOTATATE PRRT. The primary endpoint was a MM objective response rate (ORR) of less than 5%. Secondary endpoints were metabolic response, MM-related safety, and clinical response, as well as MM progression-free survival (PFS) and non-MM PFS. Results: In total, 52 patients were included. The MM ORR was 4% (n = 2), and the non-MM ORR was 8% (n = 4). No patient had a MM metabolic response, and the non-MM metabolic response rate was 12% (n = 6). Among the 26 patients with baseline MM-related symptoms, 46% had a clinical response. Four patients presented with gastrointestinal complications during PRRT. The median MM-related PFS was not reached, and the non-MM PFS was 50.3 mo (95% CI, 38.2-61.7 mo). Conclusion: This study confirms that 177Lu-DOTATATE PRRT does not lead to morphologic response on MMs (ORR < 5%). However, it allows MM stability, with few MM-related side effects, and has a relevant impact on MM-related symptoms.

Value of Somatostatin Receptor PET/CT in Patients With MEN1 at Various Stages of Their Disease.

CONTEXT: Despite the growing evidence of the clinical value of somatostatin receptor (SSTR) positron emission tomography (PET) in the evaluation of neuroendocrine tumors (NETs), its role remains to be clarified at different time points in the journey of patients with multiple endocrine neoplasia type 1 (MEN1). The rarity of the disease is however a significant impediment to prospective clinical trials. OBJECTIVE: The goals of the study were to assess the indications and value of SSTR PET/computed tomography (CT) in patients with MEN1. METHODS: We retrospectively included patients from 7 French expert centers for whom data on SSTR PET/CT and morphological imaging performed at the same period were available. Detection rates of PET study were analyzed. RESULTS: One hundred and 8 patients were included. SSTR PET/CT was performed at screening (n = 33), staging (n = 34), restaging (n = 37), and for peptide receptor targeted radiotherapy selection (n = 4). PET detected positive pancreatic lesions in 91% of cases at screening, with results comparable with magnetic resonance imaging but superior to CT (P = .049). Metastases (mostly lymph node [LN]) were present at the screening phase in 28% of cases, possibly due to the suboptimal value of screening morphological imaging in the assessment of nodal metastases and/or a long delay between imaging studies. SSTR PET/CT was considered superior or complementary to the reference standard in the assessment of LN or distant metastases in the vast majority of cases and regardless of the clinical scenario. CONCLUSION: This study shows the potential added value of SSTR PET in the assessment of MEN1-associated NETs and provides great impetus toward its implementation in the evaluation of patients with MEN1.

Peptide Receptor Radionuclide Therapy by 177Lu-DOTATATE of a Secreting Cervical Paraganglioma.

ABSTRACT: A 59-year-old man with a parapharyngeal paraganglioma incidentally discovered on a cervical swelling was referred to our nuclear medicine department for a morpho-metabolic assessment. An 18F-FDG PET/CT was initially performed and found an intense hypermetabolism of the lesion and a hypermetabolism of the periadrenal brown fat evoking catecholamine secretion. An additional 68Ga-DOTATOC PET/CT was performed, showing an overexpression of the somatostatin receptors of this isolated paraganglioma. After multidisciplinary discussion, a peptide receptor radionuclide therapy with somatostatin analogs using 177Lu-DOTATATE as a compassionate measure was carried out.