Objective: To address the role of serum g-glutamyl transferase (GGT) as a marker of metastases in patients with renal cell carcinoma. Methods: Serum alkaline phosphatase and GGT were determined in 156 patients with localized renal cell carcinoma and 60 patients with metastases as proven by echosonography, computerized tomography and bone scan. The control group consisted of 50 healthy subjects matched for sex and age. Sensitivity and specificity of both enzymes as markers of metastatic disease were compared. In metastatic patients, enzyme activities were analyzed according to the site of metastases. Results: Both alkaline phosphatase and GGT activities were normal in majority of patients with localized renal cell carcinoma and increased in most of the patients with metastatic disease (80% and 70%, respectively). GGT did not significantly differ from alkaline phosphatase in terms of sensitivity (70% vs 80%) and specificity (89% vs 92%). Concerning the site of metastases, high frequencies of increased GGT and alkaline phosphatase were found in patients with liver-only metastases (80% and 90%, respectively). All of the patients with both liver and bone metastases exhibited increased activity of both enzymes. Despite the fact that bone cells do not express GGT, increased activity was found in patients with bone metastases-only (45%), suggesting that enzymes might be released from tumor cells. Conclusions: Our data provided evidence that GGT is a sensitive marker of metastatic renal cell carcinoma. However, findings of abnormal GGT activity cannot specify the site of involvement.
