Prognostic significance of urinary antigen analysis by enzyme-linked immunosorbent assay in melanoma patients.

Urine samples collected from normal donors and melanoma patients were analyzed for the presence of tumor-associated antigen by competitive inhibition in the enzyme-linked immunosorbent assay (ELISA) using an allogeneic melanoma serum as the source of antibody and partially purified urine from the same donor as the target antigen. The results were expressed as antigen units (ng antigen protein/mg creatinine). The antigen levels in urine of melanoma patients (median = 56.5, N = 56) were significantly higher (P less than 0.05) than those of normal donors (median = 1.9, N = 56). The 90th percentile for the normal group was 34.3 antigen units. Using this value as the criterion for positivity, 36 of 56 (64%) urine samples of melanoma group were positive for the antigen as opposed to only 6 of 56 (11%) of normal donors. Subsequently, a retrospective analysis of 58 melanoma patients paired on the basis of disease recurrence and no recurrence after lymphadenectomy revealed a median antigen level of 68 units for the recurrent group and 18.9 for the nonrecurrent group. Eighteen of 29 (62%) melanoma patients who had recurrence of their disease and 9 of 29 (31%) patients who remained disease free were urinary antigen positive. These incidences were significantly different (P less than 0.005). The results of this investigation suggest that assessment of urinary antigen in stage I and II melanoma patients may prognosticate recurrence of the disease.