Utility of 18F-FDG-PET/CT in patients suspected of paraneoplastic neurological syndrome: importance of risk classification.

PURPOSE: To assess the diagnostic impact of 18F-FDG-PET/CT in patients suspected of paraneoplastic neurological syndrome (PNS) based on our own pre-test risk classification (PRC). METHODS: A multicenter retrospective longitudinal study was conducted from 2006 to 2014. We designed a seven-point scoring system using the clinical syndrome characteristics [classical (CS) and non-classical syndromes (NCS)] and its location (central, peripheral, in the neuromuscular junction or combined), onconeural antibodies and tumor markers. Patients were classified as low (score 0-2), intermediate (3-4) and high (5-7) pre-test risk of PNS. FDG-PET/CT was classified as negative or positive. Final diagnosis according Graus' criteria (definite, possible or no PNS) was established. Relations between clinical and metabolic variables with the final diagnosis were studied. RESULTS: 73 patients were included, with a follow-up time of 33 months. Eleven (15 %) patients were finally diagnosed with neoplasm (8 invasive cancers). Ultimately, 13 (18 %) and 24 (33 %) subjects were diagnosed as definite or possible PNS. All the patients with final diagnosis of neoplasm had a CS (p = 0.005). PET/CT was helpful to diagnose 6/8 (75 %) invasive cancers. PET/CT findings were associated with the final diagnosis of neoplasm (p = 0.003) and the diagnosis of PNS attending to Graus' criteria (p = 0.019). PRC showed significant association with the final diagnosis of neoplasm and PET/CT results. A majority of patients (10/11) diagnosed of neoplasm had intermediate/high-risk. CONCLUSIONS: Our PRC seems to be a valid tool to select candidates for PET/CT imaging in this setting. PET/CT detected malignancy in a significant proportion of patients with invasive cancer.

[(18)F-FDG PET/CT in the evaluation of patients suspected of paraneoplastic neurological syndrome]. / PET/TC con (18)F-FDG en la valoración de pacientes con sospecha de síndrome paraneoplásico neurológico.

OBJECTIVE: This study aimed to determine the diagnostic impact of (18)F-FDG PET/CT based on the clinical features of paraneoplastic neurological syndrome (PNS). MATERIAL AND METHODS: Multicenter retrospective and longitudinal study of patients with suspicion of PNS. The clinical picture was classified into classic (CS) and non-classic syndrome (NCS). After the follow-up, the definitive or possible diagnosis of PNS was established. The pictures that did not match any of the previous criteria were categorized as non-classifiable. The state of the onco-neural antibodies was studied. The PET/CT was classified as positive or negative for the detection of malignancy. The relationship between PET/CT findings and the final diagnosis was determined. The differences between variables (Pearson test X(2)) and the relationship between the results of the PET/CT and the final diagnosis were analyzed. RESULTS: A total of 64 patients were analyzed, classifying 30% as CS and 42% as NCS. After the follow-up, 20% and 16% of subjects were diagnosed as possible and definitive PNS, respectively. Positive onco-neural antibodies were found in 13% of the patients. A definitive diagnosis of PNS was associated with a positive PET/CT (P=.08). A significant relation between antibodies expression and final diagnosis of neoplasia (P=.04) was demonstrated. The PET/CT correctly localized malignancy in 5/7 cases of invasive cancer. CONCLUSIONS: The PET/CT showed a higher percentage of positive results in patients with definitive diagnosis of PNS. Despite the low prevalence of malignancy in our series, the PET/CT detected malignancy in a significant proportion of patients with invasive cancer.