Clinical evaluation of 5-S-cysteinyldopa testing using a new and optimized detection system as a tumour marker for malignant melanoma

5-S-cysteinyldopa (5-S-CD) has been described as a tumour marker for the detection of human metastatic melanoma. We investigated the clinical utility of a new and optimized method to detect 5-S-CD by analysing 207 plasma samples derived from 138 patients with clinical stage I/II ( = 60), III ( = 32) or IV ( = 46) melanoma. Control groups consisted of 27 patients with non-melanoma skin diseases and 30 healthy volunteers. 5-S-CD plasma levels were determined using a new analytical technique based on a fully automated solid phase extraction coupled online to a novel high performance liquid chromatography method. In all the samples from the healthy control subjects 5-S-CD plasma concentrations were below 2.0 microg/l. Increased 5-S-CD-levels (>/=2.0 microg/l) were found in 52%, 67% and 81% of the plasma samples from patients with stages I/II, III and IV malignant melanoma, respectively. The mean values of 5-S-CD were found to rise with increasing tumour stage. Among 27 samples from patients with non-melanoma skin disease, slightly elevated 5-S-CD levels between 2.3 and 2.6 microg/l were found in only four samples from patients with multiple dysplastic naevi. In conclusion, our improved analytical technique provides a high sensitivity in all stages of the disease and represents a useful technique for monitoring melanoma patients.