Prognostic significance of the detection of circulating malignant cells by reverse transcriptase-polymerase chain reaction in long-term clinically disease-free melanoma patients.

The purpose of this study was to assess the prognostic significance of the detection of circulating melanoma cells by reverse transcriptase-PCR in long-term clinically disease-free melanoma patients. Patients with melanoma who were free of clinical relapse for at least 6 months after primary tumor diagnosis were included and prospectively followed. Tyrosinase mRNA in peripheral blood from these patients was assayed by reverse transcriptase-PCR at the time of their inclusion in the study. One hundred six blood samples from 57 melanoma patients were analyzed. The median time between melanoma diagnosis and inclusion in the study was 24 months (range, 7-51 months). The median follow-up time calculated from the time of inclusion in the study was 27 months (range, 11-36 months). Tyrosinase mRNA in blood was detected in 10 (17.5%) of 57 patients: 2 (18%) of 11 stage I patients, 6 (19%) of 33 stage II patients, and 2 (15%) of 13 stage III patients. Actuarial 2-year DFS was 89% for the tyrosinase-negative patients versus 30% for the positive patients (P = 0.003). Actuarial 2-year OS was 97% for the tyrosinase-negative patients versus 72% for the positive patients (P = 0.001). Tyrosinase mRNA could be detected in the blood of a proportion of long-term disease-free melanoma patients, regardless of their initial clinical stage. The presence of late circulating melanoma cells in this selected group of clinically disease-free patients was significantly associated with a subsequent high risk of relapse and death.