Plasma markers for identifying patients with metastatic melanoma

Abstract

Purpose: With the rising incidence of melanoma, more patients are undergoing surveillance for disease recurrence. Our purpose was to study levels of proteins that might be secreted in the blood of patients with metastatic melanoma that can be used for monitoring these individuals.

Methods: Genome-wide gene expression data were used to identify abundantly expressed genes in melanoma cells that encode for proteins likely to be present in the blood of cancer patients, based on high expression levels in tumors. ELISA assays were employed to measure proteins in plasma of 216 individuals; 108 metastatic melanoma patients and 108 age- and gender-matched patients with resected stage I/II disease split into equal-sized training and test cohorts.

Results: Levels of seven markers, CEACAM (carcinoembryonic antigen-related cell adhesion molecule), ICAM-1 (intercellular adhesion molecule 1), osteopontin, MIA (melanoma inhibitory activity), GDF-15 (growth differentiation factor 15), TIMP-1 (tissue inhibitor of metalloproteinase 1), and S100B, were higher in patients with unresected stage IV disease than in patients with resected stage I/II disease. About 81% of the stage I/II patients in the training set had no marker elevation, whereas 69% of the stage IV patients had elevation of at least one marker (P < 0.0001). Receiver operating characteristic curves for the markers in combination in these two patient populations had an area under curve (AUC) of 0.79 in the training set and 0.8 in the test set. A CART (Classification and Regression Trees) model developed in the training set further improved the AUC in the test set to 0.898.

Conclusions: Plasma markers, particularly when assessed in combination, can be used to monitor patients for disease recurrence and can compliment currently used lactate dehydrogenase and imaging studies; prospective validation is warranted.

Figure 1

Means plots showing distribution on levels of ICAM-1 and OPN in the training and test sets of patients with resected stage I/II melanoma and age and gender matched patients unresected stage IV melanoma.

Figure 2

Principal components analysis for all 7 markers in patients with stage I/II resected melanoma, patients with unresected stage IV melanoma and age and gender matched healthy individuals showing clear separation of the many of the stage IV patients from the healthy individuals and patients with resected, early stage disease.

Figure 3

Distribution of number of markers with high levels in training set (panels A and B) and test set (panels C and D) showing clear differences between patients with stage I/II resected disease and stage IV unresected disease.

Figure 4

Receiver operating characteristic curves for the training set (A) and the test set (B) showing an area under the curve of 0.84 for both sets. Classification and Regression Tree (CART) analysis of the training set generating a model that uses three variables (ICAM-1, GDF-15 and OPN) to differentiate between patients with resected stage I/II disease and unresected stage IV disease (C). The model was validated in the test set with high sensitivity, specificity and AUC and a low misclassification rate (D).