Utility of FDG-PET Imaging for Risk Stratification of Pancreatic Neuroendocrine Tumors in MEN1

CONTEXT

Patients with multiple endocrine neoplasia type 1 (MEN1) are at high risk of malignant pancreatic neuroendocrine tumors (pNETs). Structural imaging is typically used to screen for pNETs but is suboptimal for stratifying malignant potential.

OBJECTIVE

To determine the utility of fluorodeoxyglucose (18F) positron emission tomography/computed tomography (18F-FDG PET/CT) for predicting the malignant potential of pNETs in MEN1.

DESIGN

Retrospective observational study.

SETTING

Tertiary referral hospital.

PATIENTS

Forty-nine adult patients with MEN1 carrying a common MEN1 mutation who underwent 18F-FDG PET/CT for MEN1 surveillance between 1 January 2010 and 30 September 2016.

INTERVENTIONS

Structural and functional imaging (magnetic resonance imaging, CT, ultrasonography, and 18F-FDG PET/CT) and surgical histopathology.

MAIN OUTCOME MEASURES

pNET size, behavior, and histopathology.

RESULTS

Twenty-five (51.0%) of 49 patients studied had pancreatic lesions on structural imaging. Five (25%) of these had 18F-FDG-PET-avid lesions. In addition, two had solitary FDG-avid liver lesions, and one a pancreatic focus without structural correlate. Eight patients with pNETs underwent surgery (three FDG-avid lesions and five nonavid pNETs). The Ki-67 index was ≥5% in FDG-avid pNETs and <2% in nonavid pNETs. Overall, six of the eight (75%) patients with FDG-avid hepatopancreatic lesions harbored aggressive or metastatic NETs compared with one of 41 patients (2.4%) without hepatopancreatic FDG avidity [P < 0.001; sensitivity; 85.7% (95% confidence interval [CI], 48.7% to 99.3%); specificity, 95.2% (95% CI, 84.2% to 99.2%)].

CONCLUSION

18F-FDG PET/CT is an effective screening modality in MEN1 for identifying pNETs of increased malignant potential. Surgical resection is recommended for FDG-avid pNETs.

Utility of FDG-PET imaging in screening for succinate dehydrogenase B and D mutation-related lesions

OBJECTIVE

Mutations of the genes encoding succinate dehydrogenase B and D (SDHB, SDHD) are associated with highly penetrant phenotypes, including paragangliomas and phaeochromocytomas. Patients with these mutations require lifelong surveillance; however, there is currently ambiguity regarding the optimal screening regimen. We sought to determine the utility of fluorodeoxyglucose (18F) positron emission tomography (18F-FDG PET) imaging, compared to other modalities for detecting SDHB and SDHD mutation-related lesions.

DESIGN

A retrospective audit of patients with SDHB or SDHD mutation.

PATIENTS

All adult patients with confirmed SDHB and SDHD mutations who underwent 18F-FDG PET/CT at our institution between 1 July 2011 and 30 May 2015.

MEASUREMENTS

18F-FDG PET/computed tomography (CT) performed during surveillance of patients with SDHB and SDHD mutations. Lesion numbers and locations detected by 18F-FDG PET were compared to those identified on the CT component, as well as other imaging modalities and histology when available.

RESULTS

Thirty-one 18F-FDG PET/CT studies were completed on 22 patients. For SDHB (20 patients), there were five positive and 21 negative studies. There were no false-negative 18F-FDG PET studies. Positive 18F-FDG PET findings correlated with magnetic resonance imaging (MRI), CT and [68 Ga]-DOTA(0)-Tyr(3)-octreotate (68 Ga DOTATATE PET/CT) imaging with no missed lesions; the only potential false-positive result relating to nonspecific postoperative changes (sensitivity 100·0%, specificity 95·5%). For SDHD (two patients), lesions were detected on 18F-FDG PET and correlated with other imaging in three of five studies. Metastatic lesions were incompletely visualized on 18F-FDG PET but were detected on the noncontrast fusion CT.

CONCLUSIONS

18F-FDG PET/CT is suitable for detecting SDHB and SDHD mutation-related lesions and may be considered effective for periodic surveillance of patients with these mutations.