Use of the copper/zinc ratio in the diagnosis of lung cancer.

Serum zinc (Zn), copper (Cu), and the Cu/Zn ratio were evaluated in 84 patients with pulmonary lesions before surgery and in 100 healthy normal controls. There were 20 patients with benign and 64 with malignant lung tumors. Only the mean (+/- SD) Cu/Zn ratio was significantly higher in malignant tumors (2.24 +/- 0.78) than in benign tissue (1.63 +/- 0.33) (P less than 0.001). In the normal group, the Cu/Zn ratio was significantly lower (1.43 +/- 0.29). Patients with advanced disease (Stage III) had higher Cu/Zn ratio than patients in Stages I and II (2.65 +/- 0.86 versus 1.9 +/- 0.27) (P less than 0.001). At a cutoff value of 1.72, Cu/Zn ratio had a sensitivity of 89%, specificity of 84%, positive predictive value of 78%, and negative predictive value of 92% between controls and lung cancer patients. Between lung cancer patients and patients with benign pulmonary lesions the aforementioned values were 89%, 70%, 90%, and 70% respectively. A correlation between increasing Cu/Zn ratio and tumor extension and postoperative survival was observed. These findings suggest that Cu/Zn ratio may be used as a diagnostic test in lung cancer patients.