Serum immunoreactive calcitonin in lung cancer

Serum immunoreactive calcitonin (iCT) assay was performed in 92 patients suffering from different kinds of cancer of the lung and in 42 healthy control subjects. Gel filtration of serum of patients suffering from microcytoma was carried out on Sephadex G75 to study the forms of circulating iCT. The obtained results (pg/ml M +/- SE) were: 1) normal subjects, 73 +/- 3; 2) epidermoidal cancer, 105 +/- 19; 3) adenocarcinoma, 116 +/- 47; 4) anaplastic carcinoma with large cells, 156 +/- 74; 5) microcytoma , 354 +/- 74; 6) chronic obstructive bronchitis, 38 +/- 6. Gel filtration of serum of patients with microcytoma demonstrated the same behavior as in normal subjects. We can conclude that iCT increases significantly in microcytoma with extensive disease (84% of cases): in this condition, the iCT assay can be useful as a marker in follow-up of disease.