Editorials: elevated plasma calcitonin as a marker for bronchogenic carcinoma.

he observation of ectopic synthesis and secretion polypeptide hormones by nonendo, tumors has been reported with increasing frequency in the past decade. Carcinomas of the lung have been particularly versatile in this regard. Reports have included corticotropin ( adrenocorticotropic hormone) and vasopressin found in some oat-cell carcinomas, gonadotropins predominantly in large-cell carcinomas, growth hormone in anaplastic carcinomas and adenocarcinomas, and parathyroid hormone predominantly in sauamous-cell carcinomas of the-lung;' howeier, thi observed incidence of hormone production by any of these tumors has been small. In 1974, Silva et a12 described two patients with ectopic secretion of calcitonin by oat-cell carcinomas of the lung. Several reports of calcitmin production by various neoplasms have subsequently been publ i~hed .~ Milhaud et als consider the frequency of ectopic production of calcitonin by neoplasms to exceed that of parathyroid hormone, and they suggest that calcitonin may be the most common polypeptide hormone produced by tumor cells which embryologically originate from the neural crest. Therefore, elevated plasma calcitonin levels may indicate the presence of tumors of this origin. The paper by Silva et al in this issue of Chest (see page 495) sheds further light on this subject. These investigators found that 62 percent (16) of 26 patients with bronchogenic carcinoma had elevated plasma levels of calcitonin, as determined by radioimmunoassay. The incidence of increased calcitonin levels was much greater in small-cell carcinoma and adenocarcinoma than in the epidermoid type. In several patients, the calcitonin levels varied directly with exacerbation and regression of the neoplastic disease. These data suggest the interesting possibility that hypercalcitoninemia may be an important "marker" in discovering early bronchogenic carcinoma and in drawing inferences as to the histologic type of the tumor. Serial calcitonin determinations could have prognostic value in evaluating exacerbations and regressions, especially in response to therapy. Further studies are necessary by multiple investigators to fully clanfy and evaluate the validity of these suggestions. Silva et a1 emphasize the importance of additional observations and have a long-term study underway. Hopefully, the endocrinologists' interest in the honnone calcitonin, and their rather recently developed radioirnmunoassay for human calcitonin can also serve the oncologist and chest physician in their diagnosis and treatment of pulmonary neoplasms.