Urine excretion of 5-S-cysteinyldopa and serum sialic acid as tumor markers in human melanomas.

This study examines 5-S-cysteinyldopa, which is a melanoma-associated marker, and sialic acid whose increase appears to be a common feature of numerous cancers. In spite of some interferences due to sun exposure, 5-S-cysteinyldopa seems a significant indicator of metastases; the difference between 46 metastasis-negative and 34 metastasis-positive melanomas is significant at P less than 0.001. Cerebral metastases give little or no increase. In contrast with the 75% of patients who keep normal 5-S-cysteinyldopa excretion, all melanoma patients have elevated sialic acid. No difference occurs between glycoprotein carbohydrates of controls and patients after pronase digestion and con A chromatography. The use of those two parameters in association is proposed to have a proper index of tumor burden or success of therapy.