Association of PD-L1 expression in melanoma with response and prognosis to ipilimumab.

9044 Background: Immunotherapy with ipilimumab demonstrated a statistically significant survival benefit. In two large phase III trials responses were observed in 10-15% of patients. However, 64% of patients exhibited significant and 20% of the patients severe grade 3 and 4 side effects. Identifying predictive biomarker profiles could enable better treatment allocation. Methods: In this multicenter study 176 tumor samples from 125 patients with metastatic melanoma were analyzed for PD-L1 gene expression, thereof 78 patients had received ipilimumab (30 responders and 48 non-responders). mRNA was extracted from formalin-fixed paraffin embedded (FFPE) tumor tissue by a fully automated method and measured by quantitative RT-PCR. Differences of survival and PD-L1 expression between patient groups were assessed using the Mann-Whitney U test, the logrank test and the Kaplan-Meier technique. Results: Patients with low PD-L1 expression showed a significantly better survival than those with high expression of PD-L1...