Patients and Methods: A PCR assay that uses four melanoma-associated gene markers (tyrosinase, pay, MUC18, and MAGE-3) wets developed. Sensitivity and specificity of the PCR assay for individual markers were assessed using 10 melanoma cell lines and peripheral-blood lymphocytes (PBL) from 39 normal volunteers as controls. The assay's sensitivity and specificity were improved using nested primers and Southern blot analysis. Patients (N = 119) with American Joint Committee on Cancer (AJCC) stages I to IV disease were evaluated for circulating melanoma cells using the four gene markers under optimal conditions.

Results: All melanoma-associated gene markers were expressed in at least 80% of the melanoma lines, whereas 37 of 39 normal PBL tested negative for all markers; the remaining two PBL were positive for MUC18. Using four markers in the PCR assay was significantly better than using tyrosinase alone. There wets a significant correlation between the number of positive PCR markers, AJCC stage of disease, and progression of disease. In all AJCC stages, there were more PCR-positive patients with disease than without disease.

Conclusion: A multimarker PCR assay is more reliable and sensitive than ct single-marker assay for detection of melanoma cells in blood of patients. This assay can provide important insight into tumor progression kinetics without major surgical or conventional radiologic diagnostic procedures. (C) 1995 by American Society of Clinical Oncology.