Typical bronchial NETs as a misleading biology.

Abstract

8528 Background: Bronchial Neuroendocrine tumours (NETs) are rare with an incidence of between 0.2 – 2 per 100,000 population. There has been an increase in prevalence due to increased awareness, enhanced immunohistochemistry and greater use of Computed tomography (CT). Bronchial NETs are classified according to the WHO guidelines developed in 2004 where they are graded by histological classification into ‘typical’, ‘atypical’ NETs or small and large neuroendocrine carcinoma’s (NECs). Typical NETs are regarded as being low-grade malignant however metastatic disease can still develop. Aims: We sought to determine the incidence of metastatic typical bronchial NETs, their survival and investigate the imaging and treatment used in their management. Methods: We performed a retrospective analysis of all bronchial NETs managed at our centre from 2001 to 2016. From those identified as typical NETs, we analysed clinical records in those with advanced disease (Stage IV). Results: From a total of 251 bronchial NETs, there were 147 ‘Typical’ NETs, 30(20%) of whom had advanced disease compared to 82 'Atypical' bronchial NETs of whom 55 had advanced disease (67%). The median age at diagnosis was 58 (range 24-77). In the 'Typical' NETs, 24/30 had liver metastases, 19/30 skeletal metastases, and 16 had carcinoid syndrome (CS). Functional imaging with FDG PET scan was positive in 7/10 patients and somatostatin receptor scintigraphy (SRS) positive in 16/20 and in 4/11 there was avidity with both. 20 patients were treated with somatostatin analogues predominantly for CS symptoms. 11 patients treated with peptide radiolabelled receptor targeted therapy (PRRT) with a median Time-To-Progression (TTP) of 27 months. 11 patients received chemotherapy with median TTP of 16 months with 4 patients demonstrating partial response. Conclusions: Typical bronchial NETs can lead to advanced disease in up to 20% of patients. Their behavior can be aggressive and is not predictable by histology alone. Functional imaging with both FDG and SRS may help determine the most appropriate treatment. Both PRRT and chemotherapy can be considered in progressive disease.