Background: MIA and S-100 have been proposed as tumor markers for patients with melanoma, but they are not widely accepted. BRAF V600E mutation has been reported in more than 50% of melanomas. Recently, selective BRAF inhibitors have proved to be more active than DTIC in first line treatment of BRAF V600E melanoma patients. The aim of the present work is to evaluate the utility of MIA and S-100 during iBRAF treatment. Methods: BRAF V600E mutation was analyzed in 77 patients with metastatic melanoma by automated direct sequencing in tumor DNA. Tumor markers (MIA, S-100 and LDH) were studied in serum from all patients. Sixteen of these patients received iBRAF therapy (11 Vemurafenib, 5 Dabrafenib) and tumor markers were analyzed sequentially: baseline, best response and progression. MIA and S-100 were determined by immunometric methods and LDH by a spectrophotometric assay. The cut-off points were MIA=9 ug/L, S-100=0.1 ug/L, and LDH=290 U/L. Non-parametric statistical analysis was performed. Results: Forty-three patients had BRAF V600E mutation and 34 were wild type (WT). The percentage of cases with MIA above the cut-off in patients with V600E mutation was significantly higher than in the WT group (76.3% vs. 52.9%; p<0.05), while the frequency of elevated S-100 and LDH was similar. Among patients treated with iBRAF, the response rate was 87.5% (5 CR, 9PR). In responding patients, MIA and S100 levels decreased dramatically, but not LDH (Table). At the time of this report, thirteen patients have progressed. Upon progression, MIA and S-100 increased significantly above levels achieved at best response (Table). Conclusions: Serum MIA and S-100 are potentially useful markers in the clinical and follow-up management of patients receiving iBRAF therapy. Validation in a larger series is needed.

M: Median. NS: no significant.