[Plasma DNA level as a tumor marker in primary lung cancer]

The plasma level of human DNA was determined by the dot-hybridization method using human Alu-family DNA as a probe in 45 patients with primary lung cancer, 54 patients with benign pulmonary diseases, and 59 healthy controls. The mean plasma DNA level was significantly higher in the patients with lung cancer than that in the patients with benign pulmonary diseases or in healthy controls. The mean plasma DNA level in the patients with benign pulmonary diseases was also significantly higher than that in healthy controls. There was no significant difference in mean plasma DNA level in each histologic type of lung cancer. The plasma DNA level was elevated above the cut-off level of 80 ng/ml in 71% of the patients with lung cancer, 37% of the patients with benign pulmonary diseases and none of the healthy controls. The serum CEA was positive in 38% of the patients with lung cancer and thus when plasma DNA and serum CEA were used in combination, 78% of the cases with lung cancer could be detected by these two markers. In the patients with lung cancer who responded to treatment, the plasma DNA levels were significantly decreased after treatment, while its levels were elevated in the patients whose treatment was unsuccessful. These findings indicate that plasma DNA may be a useful marker in patients with lung cancer.