Molecular identification of bronchopulmonary neuroendocrine tumours and neuroendocrine genotype in lung neoplasia using the NETest liquid biopsy

OBJECTIVES: Diagnosing lung neuroendocrine neoplasia (NEN) requires a biopsy or an operation. We evaluated a 'liquid biopsy' (NETest) as an in vitro diagnostic tool for identifying NEN and compared it to chromogranin A (CgA). METHODS: We identified 4 study cohorts: Patients with bronchopulmonary carcinoids (n = 99, including 62 typical and 37 atypical carcinoids), lung cancers [n = 101, including 41 adenocarcinomas, 37 squamous carcinomas (SQC), 16 small-cell lung cancers and 7 large-cell neuroendocrine carcinomas]; benign disease (50 idiopathic pulmonary fibrosis) and healthy controls (n = 102). Transcript levels measured quantitatively (activity scores: 0-100) were compared to CgA (enzyme-linked immunosorbent assay; normal < 109 ng/ml) levels. RESULTS: The results of the NETest were positive (>20) in 94% of patients with bronchopulmonary carcinoid compared to 8% of the controls (Fisher's exact test; P < 0.001) and were significantly more accurate as a diagnostic test (McNemar's test; P < 0.001, χ2 = 72) than was CgA (positive: 19% bronchopulmonary carcinoid, 15% controls). Small-cell lung cancers (87%), large-cell neuroendocrine carcinomas (86%), adenocarcinoma (42%) and SQC (35%) were also NETest-positive. Increasing the NETest cut-off score to >40 was useful for detecting all NENs and differentiating these tumours from either controls/benign lung diseases (specificity 97%) or adenocarcinoma/SQC (specificity 94%). CgA was positive in 15-44% irrespective of pathology and had no diagnostic value. CONCLUSIONS: A gene-based liquid biopsy is an effective and accurate method for diagnosing lung tumours with neuroendocrine gene expression. CgA has no value. An NETest score >40 provides an accurate (94-97%) rule-in for the diagnosis of NEN and a rule-out for benign and other neoplastic diseases. Because neuroendocrine gene expression is associated with a poor prognosis, NETest levels may have utility both in the diagnosis of and the treatment stratification for lung neoplasia.