Baseline relative eosinophil count as a predictive biomarker for ipilimumab treatment in advanced melanoma

// Pier Francesco Ferrucci 1 , Sara Gandini 2 , Emilia Cocorocchio 1 , Laura Pala 1 , Federica Baldini 3 , Massimo Mosconi 3 , Gian Carlo Antonini Cappellini 4 , Elena Albertazzi 2 and Chiara Martinoli 1 1 Medical Oncology of Melanoma Unit, Division of Medical Oncology of Melanoma and Sarcoma, European Institute of Oncology, Milan, Italy 2 Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan, Italy 3 Division of Surgery of Melanoma and Sarcoma, European Institute of Oncology, Milan, Italy 4 IV Oncology Division, Istituto Dermopatico dell’Immacolata IRCCS, Rome, Italy Correspondence to: Pier Francesco Ferrucci, email: pier.ferrucci@ieo.it Keywords: eosinophil, predictive, biomarker, ipilimumab, melanoma Received: May 17, 2017 Accepted: June 30, 2017 Published: August 01, 2017 ABSTRACT As diverse therapeutic options are now available for advanced melanoma patients, predictive markers that may assist treatment decision are needed. A model based on baseline serum lactate dehydrogenase (LDH), peripheral blood relative lymphocyte counts (RLC) and eosinophil counts (REC) and pattern of distant metastasis, has been recently proposed for pembrolizumab-treated patients. Here, we applied this model to advanced melanoma patients receiving chemotherapy ( n = 116) or anti-CTLA-4 therapy ( n = 128). Visceral involvement, LDH and RLC were associated with prognosis regardless of treatment. Instead, when compared to chemotherapy-treated patients with REC < 1.5%, those with REC ≥ 1.5% had improved overall survival when receiving anti-CTLA-4 [Hazard Ratio (HR) = 0.56 (0.4–0.93)] but not chemotherapy [HR = 1.13, (0.74–1.74)], and the treatment-by-REC interaction was significant for both overall ( p = 0.04) and progression free survival ( p = 0.009). These results indicate baseline REC ≥ 1.5% as a candidate predictive biomarker for benefit from anti-CTLA-4. Further studies are needed to confirm these findings in patients receiving immune-modulating agents.