Elevated gamma-glutamyl transpeptidase levels in malignant melanoma

Serum gamma(glutamyl) transpeptidase (GGTP) levels were measured in fifty patients with malignant melanoma to determine whether the enzyme was a sensitive indicator of disease status. Patients were divided into three groups based on clinical stage. Eighteen patients, following complete surgical resection of their primary disease, had a mean GGTP value of 10.97 International Units/Liter, which was not significantly different from the mean of healthy controls (10.2 +/- 2.5; range, 5.56--15.2). Likewise, eight patients who had undergone resection of regional disease or solitary metastasis had values near the upper range for controls. Serial testing in 15 of the above patients revealed no significant fluctuations on a daily or monthly basis. In contrast, individuals with metastatic disease had significantly elevated GGTP levels and demonstrated stepwise increases with disease progression. In seven patients enzyme levels were predictive of either recurrent disease or response to therapy. We conclude that serum GGTP levels are a useful test in monitoring clinical status of melanoma patients.