Biomarkers have long held out the promise that malignancies might be diagnosed early and that patients could be monitored more confidently during their clinical course to more reliably predict recurrence and the effect of therapy. Reliable tumor markers have been described for colon carcinoma, hepatomas, and other tumors, but no reliable marker has been identified to monitor the course of malignant melanoma. Recently, the plasma level of lipid-bound sialic acid (LASA-P) has been described as reflecting an alteration in the surface membrane of cancer cells. An attempt was made to correlate the LASA-P level, along with the serum level of neuron-specific enolase, a glycolylic enzyme specific to cells of neuroectoderm origin including melanocytes, with clinical disease activity with a follow-up to at least 2 years. Two hundred seventy patients had blood samples drawn at various times during their clinical course for assay of LASA-P and neuron-specific enolase. Eighty of the patients (30%) sampled developed a recurrence sometime during their clinical course, whereas another 10 patients had active disease noted at diagnosis with evaluative tumor markers. The sensitivity and specificity of neuron-specific enolase was 27% and 77%, respectively, and cannot be recommended as a marker for melanoma. LASA-P showed a sensitivity of 65%, with 55 patients recurring and having active disease with abnormally high markers and 35 patients recurring or having active disease with normal markers. Specificity of the LASA-P test was 76%. When recurrence was associated with elevated LASA-P levels, the elevated level preceded recurrence by a median of 9.3 months. LASA-P may be a useful marker to follow patients with malignant melanoma.
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