An assessment of 18 F-FDG PET/CT for thoracic screening and risk stratification of pulmonary nodules in multiple endocrine neoplasia type 1.

Context: Bronchopulmonary neuroendocrine tumours (bpNETs) and thymic carcinoid (ThC) are features of multiple endocrine neoplasia type 1 (MEN 1), and surveillance guidelines recommend periodic thoracic imaging. The optimal thoracic imaging modality and screening frequency remain uncertain as does the prognosis of small lung nodules when identified. Objectives: To evaluate fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT) for identification and prognostic assessment of thoracic lesions in MEN 1.

Design: Retrospective observational study. Setting and participants: Fifty consecutive MEN 1 patients undergoing screening with 18 F-FDG PET/CT at a tertiary referral hospital between July 2011 and December 2016. Interventions: 18 F-FDG PET/CT. Outcome measures: Pulmonary and thymic lesion prevalence, size, functional characteristics and behaviour.

Results: Thirteen patients (26.0%) exhibited pulmonary nodules with multiple nodules identified in nine (18.0%). An asymptomatic 31 mm FDG-avid ThC was identified in one patient (2%). Of the 13 patients with pulmonary nodules, four (8.0%) exhibited 13 FDG-avid nodules (mean size 10.1 ± 9.1 mm), and nine (18.0%) demonstrated 26 FDG nonavid nodules (mean size 6.9 ± 5.8 mm). All FDG-avid lesions increased in size vs 11 (42.3%) FDG nonavid lesions (P = .0004). For FDG-avid and nonavid nodules, the median doubling time was 24.2 months (IQR 11.4-40.7) and 48.6 months (IQR 37.0-72.2), respectively. Nodule resection was undertaken in two patients, typical bronchial carcinoid diagnosed in one (FDG nonavid) and metastatic renal cell carcinoma in the second (FDG avid).

Conclusion: Thoracic imaging with 18 F-FDG PET/CT effectively identifies pulmonary nodules and ThC. FDG-avid pulmonary lesions are significantly more likely to progress than nonavid lesions.