Serum S100B levels correlate with clinical benefit in a metastatic melanoma patient treated by CTLA-4 blockade: a case report.

Background: Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is an immunoregulatory molecule expressed by activated T cells. In patients with metastatic melanoma, anti-CTLA-4 antibody therapy with ipilimumab achieves durable cancer regression in approximately 10-15% of patients. In the face of complex and sometimes delayed tumor response patterns, prognostic and predictive biomarkers are needed to monitor therapy outcomes and to identify early potential long-term survivors who might also benefit from therapy re-induction.

Case report: The clinical case of a 49-year-old male patient with metastatic melanoma and unfavorable prognostic factors is presented. The time course of the serum biomarker S100B during initial anti-CTLA-4 therapy correlated very well with the clinical situation and, in the present case, proved its potential value as an early biomarker of a subsequently observed radiological response in this stage IV melanoma patient. The observed clinical response lasted for more than 24 months.

Conclusions: Further efforts are required to better understand the patterns of response and the immunological tumor response in patients undergoing CTLA-4 blockade. A validation of S100B as a marker to identify early long-term responders among patients treated with ipilimumab is warranted.