DETECTION OF OCCULT MELANOMA-CELLS IN BLOOD WITH A MULTIPLE-MARKER POLYMERASE CHAIN-REACTION ASSAY

Purpose: The objective of the study was to develop a sensitive multima rker polymerase chain reaction (PCR) assay to detect circulating melan oma cells in patient blood. The rationale was that malignant melanoma is heterogeneous in regards to antigen expression. Patients and Method s: A PCR assay that uses four melanoma-associated gene markers (tyrosi nase, pay, MUC18, and MAGE-3) wets developed. Sensitivity and specific ity of the PCR assay for individual markers were assessed using 10 mel anoma 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 d isease were evaluated for circulating melanoma cells using the four ge ne markers under optimal conditions. Results: All melanoma-associated gene markers were expressed in at least 80% of the melanoma lines, whe reas 37 of 39 normal PBL tested negative for all markers; the remainin g two PBL were positive for MUC18. Using four markers in the PCR assay was significantly better than using tyrosinase alone. There wets a si gnificant correlation between the number of positive PCR markers, AJCC stage of disease, and progression of disease. In all AJCC stages, the re were more PCR-positive patients with disease than without disease. Conclusion: A multimarker PCR assay is more reliable and sensitive tha n ct single-marker assay for detection of melanoma cells in blood of p atients. This assay can provide important insight into tumor progressi on kinetics without major surgical or conventional radiologic diagnost ic procedures. (C) 1995 by American Society of Clinical Oncology.