POLYMERASE CHAIN-REACTION DETECTION OF CIRCULATING MELANOCYTES AS A PROGNOSTIC MARKER IN PATIENTS WITH MELANOMA

Background end Design: Polymerase chain reaction (PCR) detection of ci rculating tumor cells from malignant melanoma (MM) was recently descri bed, but the prognostic value of this method in the treatment of patie nts with MM remained unclear. In the present prospective study, blood samples (n=193) were collected from 93 patients with MM: 10 stage I pa tients after primary tumor resection, 18 patients with regional, lymph node metastases before node resection, 33 disease-free but highrisk p atients (previously treated for node metastases), and 32 patients with distant metastases. Circulating melanocytes were detected using a rev erse transcriptase PCR method that analyzes tyrosinase gene expression . All patients were kept under regular surveillance. Results: The PCR assay was always negative in normal individuals and in subjects with n on-MM metastatic cancer, while it was positive in 16 of 32 patients wi th disseminated MM. Five of eight patients who were PCR-positive befor e node dissection vs one of 10 who were PCR-negative relapsed within 6 months after surgery. In highrisk but apparently disease-free patient s, the risk of relapse within the next 6 months was 3.8 times higher a fter a positive test result. In patients with distant metastases, a po sitive PCR predicted rapid disease progression. Conclusions: These dat a suggest that PCR detection of circulating melanocytes can be conside red as a marker for rapid postoperative relapse after node dissection in patients with MM with regional node metastases, for shortterm relap se in high-risk disease-free patients, and for rapid and severe progre ssion in patients with distant metastases. This test may have a crucia l interest in the treatment of patients with MM.