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Mammalian Target of Rapamycin (mTOR) Inhibition in Advanced Bronchial Carcinoids

European Oncology & Haematology, 2015;11(2):100–4 DOI:


Bronchial carcinoids (BCs), comprising typical (TC) and atypical (AC) carcinoids, account for 1–2 % of all lung cancers and approximately 20–30 % of all neuroendocrine neoplasms (NENs). They represent the low- and intermediate-grade lung NENs, whereas small cell lung carcinoma (SCLC) and large cell neuroendocrine carcinoma (LCNEC) represent the high-grade entities. While the prognosis of BCs is favourable at early stages, it is poor when distant metastases are present. Unfortunately, there is a lack of therapeutic options as well as limited data to support the use of standard therapies and sequences of treatments. Some chemotherapeutic regimens have been reported to be active, but their efficacy has not been validated so far. Somatostatin analogues (SSAs) as single agents can be an option for very slow-growing disease, but their role in combination with other therapies has not been established. Among the new targeted agents, data from clinical trials showed that everolimus is a promising one.
Keywords: Lung NET, lung neuroendocrine tumour, bronchial carcinoid, carcinoid tumour, pulmonary neuroendocrine neoplasm, somatostatin analogue, small cell lung cancer, large cell neuroendocrine carcinoma, bronchopulmonary carcinoid, everolimus
Disclosure: Nicola Fazio has participated in advisory boards for Ipsen and Novartis and received research funds from Novartis. Anna Maria Frezza has nothing to disclose in relation to this article.
Received: September 21, 2015 Accepted: October 23, 2015
Correspondence: Nicola Fazio, Unit of Medical Oncology Gastrointestinal and Neuroendocrine Tumors, European Institute of Oncology, Via G Ripamonti, 435, 20141, Milan, Italy. E:
Support: This article was published with the editorial support by Novartis. The authors wrote and reviewed the drafts, critically revised scientific accuracy and approved the final version of this article.

Neuroendocrine neoplasms (NENs) are a group of rare and heterogeneous malignancies that arise from neuroendocrine cells in most organs of the body. The presence, rather than absence of symptoms due to neuropeptides or hormones hypersecretion, distinguishes NENs in functioning and non-functioning tumours, respectively. The term NEN is used to denote any type of neuroendocrine malignancies, irrespective of histological grade and clinical behaviour.1 Gastroenteropancreatic (GEP) NENs are classified as neuroendocrine tumours (NETs) and neuroendocrine carcinomas (NECs).2 Thoracic NENs, the majority of which are bronchial, are classified as carcinoids and carcinomas (see Table 1).3. 5 The terms ‘tumours’ for GEP and ‘carcinoids’ for lung represent the low/intermediate grade of malignant NENs.

Bronchial carcinoids (BCs) represent less than 3 % (1–2 % typical carcinoids [TCs] and 0.1–0.2 % atypical carcinoids [ATCs]) of all lung cancers, but they comprise around 20–30 % of all lung NENs. Small cell lung carcinoma (SCLC) is the most common lung NEN (>80 %), and accounts for 15–20 % of lung cancers, while large cell neuroendocrine carcinoma (LCNEC) is rarer, comprising 1.6–3 % of lung cancers. Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a very rare but well-recognised pre-invasive lesion for BCs.6 BCs can be associated with a hyper-secretion syndrome, although this is more commonly seen in GEP NENs. Carcinoid syndrome (fewer than 5 % of cases), related to serotonin, is the most common one, and it is usually atypical. Cushing syndrome is rarer, related to ectopic adrenocorticotropic hormone (ACTH) production.7

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Keywords: Lung NET, lung neuroendocrine tumour, bronchial carcinoid, carcinoid tumour, pulmonary neuroendocrine neoplasm, somatostatin analogue, small cell lung cancer, large cell neuroendocrine carcinoma, bronchopulmonary carcinoid, everolimus