Diagnostic value of neurotrophin expression in malignant pleural effusions

Neurotrophins (NTs) modulate the growth of human malignancies, including lung cancers. Our prospective study evaluated the accuracy of pleural NTs [nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotrophin 3 (nT3) and 4 (nT4)] levels for differentiating benign from malignant pleural exudates. Levels of NTs were measured by ELISA in 170 patients with non-neutrophilic (<50%) exudative benign or malignant pleurisies diagnosed by pleuroscopy. Fifty-nine benign (9 infections and 50 inflammatory diseases) and 111 malignant (50 extrathoracic tumors, 51 lung cancers and 10 mesotheliomas) pleural exudates were diagnosed by thoracoscopy. Levels of BDNF were significantly higher in malignant than in benign effusions [17 pg/ml (0-367) vs. 8 pg/ml (0-51), p<0.05]. ROC analysis showed an area under the curve of 0.609 (p=0.012; best threshold 44 pg/ml). Pleural BDNF levels were significantly higher in pleural metastasis of pulmonary tumors and in mesothelioma than in pleural benign effusions. Finally, a higher proportion of pleural nT3 was detected in squamous cell lung carcinoma in comparison to that in non-squamous cell lung carcinoma (72.7 vs. 10%, p<0.0001). NTs and particularly BDNF may play a role in the pathogenesis of malignant pleural effusions.