Utility of 18F-FDG PET/CT in Follow-up of Patients with Neurofibromatosis Type 1: A Clinical Registry Study of 79 Adult Patients
Maria Tanase1, Lina Djilani1, Manon Leclerc1, Mathilde Baril1, Vincent Roy2, Mathieu Blais3, François Gros-Louis2, Nicolas Dupre3
1Department of Medicine, Faculty of Medicine, Universite Laval, Quebec, Canada, 2Regenerative Medicine Division, CHU de Quebec - Universite Laval, Quebec, Canada, 3Neuroscience Division, CHU de Quebec - Universite Laval, Quebec, Canada
Objective:
The purpose of the current study is to demonstrate significant incidental findings of malignant and potentially malignant tumors with positron emission tomography/computed tomography (PET/CT) in an adult population of neurofibromatosis type 1 (NF1) patients. 
Background:
NF1 is an autosomal dominant syndrome that predisposes affected individuals to benign and malignant tumors throughout life. Early detection of malignant or pre-malignant tumors is critical, as these transformations are often associated with poor prognosis. 
Design/Methods:
In this retrospective observational study of 79 adult NF1 patients, patients' characteristics, clinical manifestations and tumor diagnoses were collected from electronic medical records. Imaging and diagnostic modalities that led to the diagnosis of NF1-related tumors and other malignant and potentially malignant tumors, including PET/CT, magnetic resonance imaging, CT, mammography, scintigraphy, and pathology, were thoroughly reviewed.  
Results:
51 patients (64.6%) underwent a PET/CT scan during their follow-up with their neurologist. A total of 31 malignant or potentially malignant tumors as well as 2 pheochromocytomas and 24 gliomas were diagnosed in our adult population, all imaging modalities combined. Notably, 12 significant findings, including 4 gastrointestinal stromal tumors, 3 carcinomas and pre-malignant tumor of the thyroid gland, 2 malignant peripheral nerve sheath tumors, 1 serous borderline ovarian tumor, 1 testicular seminoma and 1 pheochromocytoma were diagnosed incidentally by PET/CT scan. Most required surgery and could have significantly impacted disease management if diagnosed at a later stage. 
Conclusions:
In this cohort of 79 adult patients with NF1, PET/CT was a useful imaging modality in detecting incidental malignant or potentially malignant tumors when observed in comparison to other imaging and diagnostic modalities routinely prescribed in the clinic. Therefore, in addition to other whole-body imaging methods, PET/CT could contribute to improved medical monitoring in NF1-related cancers in adult patients. Early identification of malignant tumors will allow timely intervention, improving outcomes and treatment options.  
10.1212/WNL.0000000000211533
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