Interleukin-6 and its surrogate C-reactive protein are useful serum markers for monitoring metastasized malignant melanoma

Malignant melanoma cells are known to secrete interleukin-6, and elevated interleukin-6 serum levels were reported to correlate with shorter median survival rates. We, therefore, investigated serum values of interleukin-6 and its surrogate C-reactive protein for the ability to discriminate progressive from non-progressive metastatic melanoma disease. Just prior to re-staging examinations, interleukin-6, C-reactive protein and the conventional parameter lactate dehydrogenase were determined in 74 patients with stage IV malignant melanoma according to the criteria of the American Joint Committee on Cancer. We found all tested serum parameters to be significantly elevated in progressive disease. Calculating sensitivities and specificities by logistic regression analysis, the highest sensitivities, according to the established thresholds, were found for interleukin-6 and C-reactive protein with 86% and 76%, respectively. Lactate dehydrogenase had the highest specificity with 94%. Calculating Somers' D-xy rank correlation and the area under the "Receiver Operating Characteristic" curve, all three parameters showed high ability to driscriminate progressive from non-progressive disease. By multiple logistic regression, lactate dehydrogenase was identified to be the most statistically significant marker for progressive disease. We conclude that, comparable to lactate dehydrogenase, interleukin-6 and its surrogate C-reactive protein are useful serum markers for monitoring metastatic malignant melanoma.