Aim of the study: L-DOPA/tyrosine ratio (an index of tyrosinase activity), melanoma antigens S100B and MIA, lactate deshydrogenase (LDH) and their combinations were evaluated for clinical value as tumour markers in melanoma.
Methods: Blood samples were obtained in 170 melanoma patients (stage I-II: n=57, III: n=54, IV: n=59) at inclusion and in a sub-group of 82 subjects during follow-up for up to 4 years. Laboratory analyses were performed by HPLC (L-DOPA, L-tyrosine), immunoassays (S100B, MIA) and colourimetry (LDH).
Results: All markers, except LDH, were elevated in stage IV versus other stages. S100B and MIA highly correlated, especially in stage IV (r(s): 0.849, p<0.001). The combination of L-DOPA/tyrosine ratio with S100B displayed the highest sensitivity/specificity (73/70%) to confirm stage III-IV or stage IV alone (69/75%) (ROC optimised cut-off). Only the L-DOPA/tyrosine ratio significantly increased (+36% over 5 months, p=0.001) during progression from stage I-III to higher stages. S100B, MIA and LDH, but not the L-DOPA/tyrosine ratio, responded to progression towards death in stage IV. All markers exhibited a prognostic value in deceased patients (n=44); S100B and MIA were the best predictors of survival time by Cox proportional-hazards regression.
Conclusion: The combination of plasma L-DOPA/tyrosine ratio and S100B appears an attractive approach for the biological follow-up of melanoma patients.