Changes in the presence of multiple markers of circulating melanoma cells correlate with clinical outcome in patients with melanoma.

Purpose: Melanoma cells can be found in the circulation of patients with melanoma. The following study was conducted to examine whether changes in their presence could provide an early marker of response to therapy.

Experimental Design: We measured the presence of several markers of melanoma cells in the peripheral blood of 118 patients with resected stage IIb, III, or IV melanoma before and after immunotherapy with a polyvalent, shed antigen, melanoma vaccine using reverse transcription-PCR assays for tyrosinase, gp100, MART-1, and MAGE-3. Assays were conducted at baseline and after 3, 5, and 11 months of therapy.

Results: Overall, 47% of patients were positive for at least one marker during the study. Before vaccine treatment, circulating melanoma cell markers were present in 23% of patients. After 5 and 7 months of vaccine therapy, the proportion of patients with circulating markers decreased by 27% and 55%, respectively (P for trend = 0.02). The recurrence-free survival of patients whose melanoma cell markers disappeared during vaccine treatment was significantly longer than that of patients in whom they increased, i.e., the percentage of patients who were recurrence free at 1 year was 80% versus 58% (P = 0.03).

Conclusions: Therapy with a polyvalent melanoma vaccine was associated with clearance of melanoma cell markers from the circulation, and the clearance was associated with an improved prognosis. These findings suggest that the sequential assay of tumor cells in the circulation by reverse transcription-PCR may provide an early indication of the effectiveness of cancer therapy.