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Henry Ford Hospital Medical Journal

Abstract

Immunoreactive calcitonin (ICT) can be ectopically secreted by lung cancer cells and has been proposed as a tumor marker for bronchial neoplasms. Since PDN-21 (katacalcin or the carboxyl-terminal flanking peptide of the calcitonin gene) and CT are cosecreted in normal subjects and in patients with medullary thyroid carcinoma (MTC), we sought to determine the potential utility of PDN-21 as a tumor marker for lung cancer. We measured carcinoembryonic antigen (CEA), neuronspecific enolase (NSE), iCT, and PDN-21 in 119 to 378 healthy subjects, 88 to 91 patients with benign pulmonary diseases, and 249 patients with advanced lung cancer (108 small cell lung cancers and 141 other forms). Tumor marker specificity was satisfactory: the percentage of increased values (greater than the 95th percentile of normal subjects) in patients with benign pulmonary diseases varied from 9% (NSE, PDN-21) to 12% (CEA). PDN-21 was a more sensitive marker for lung cancer than iCT; the percentage of increased values was 44% for PDN-21 versus 19% for iCT, and 51% versus 23% for the subgroup of patients with small cell lung cancer (SCLC). PDN-21 concentrations were increased in 69 (34%) of 202 patients with a normal iCT level, whereas iCT concentrations were increased in only six (4%) of 139 patients with a normal PDN-21 level. However, markedly elevated concentrations of the two markers generally occurred in the same patients and the correlation between the two markers was significant (r, = 0.60; P < 0.01). PDN-21 provided complementary information to that from the classical markers NSE and CEA. PDN-21 was thus elevated in seven (47%) of 16 patients with SCLC and a normal NSE level, and in 19 (30%) of 63 patients with non-SCLC and a normal CEA level. Immunodilution curves of sera with elevated concentrations of PDN-21 were strictly parallel to the standard curve, suggesting that the assay essentially measured authentic PDN-21. These preliminary results suggest that PDN-21 and possibly other CT gene products are worthwhile in further biologic and clinical investigations in lung cancer.

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