[Monoclonal antibodies and bronchial cancer]

Techniques of production of monoclonal antibodies (MoAb) have provided powerful tools to study biological lung cancer behavior. Immunochemistry is more sensitive than conventional light microscopy examination to detect tumour cells in sputum or pleural effusion, or small cell lung cancer metastases in bone marrow. Immunochemistry is also helpful for the differential diagnosis of carcinoma versus lymphoma or sarcoma, using antibodies directed against antigens such as cytokeratins, vimentin, EMA, LCA, SP100, CEA. In lung cancer, immunochemistry may detect neuroendocrine differentiation, or help to distinguish metastatic carcinoma from primary lung cancer. A positive immunostaining with CEA, Leu-M1, SP1, B72-3 supports the diagnosis of pleural metastatic adenocarcinoma versus mesothelioma. Immunoscintigraphy is a non invasive imaging technique which allows local and distant disease evaluation and could replace in the future the present staging work up. To evaluate the potential therapeutic efficacy of MoAbs in Lung cancer, phase I studies have been performed. Therapeutic effect is based on: 1) indirect cytotoxicity (cells are killed by ADCC or K cells) or direct cytotoxicity (MoAb are carriers of toxins, radioisotopes or drugs). 2) Immune response modulation by anti-idiotypic Ab. 3) Interferences with growth factors. Results of most of phase I trials are disappointing. Improvement of MoAb selectivity, improvement of conjugates stability, reduction of humoral response to MoAb, enhanced tumour localisation, and reduction of nonspecific captation should lead to a better efficacy.