Objectives: Treatment with trastuzumab and chemotherapy significantly improves the outcome in patients with human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer (AGC). CT-P6 (trastuzumab-pkrb; Herzuma) is a trastuzumab biosimilar approved for the treatment of HER2-positive gastric cancer. In this study, we aimed to compare the efficacy and safety of CT-P6 and reference trastuzumab as first-line treatment for HER2-positive AGC. Materials and Methods: The medical records of 102 patients with HER2-positive AGC treated with first-line trastuzumab-based chemotherapy were retrospectively reviewed. These patients were treated with either reference trastuzumab (n=72) or a biosimilar (n=30). Treatment outcomes, such as objective response rate, progression-free survival (PFS), and overall survival (OS), were compared between the reference and biosimilar groups. Results: The objective response rate of both groups (52.8% and 56.8% in the reference and biosimilar groups, respectively) were comparable ( P =0.72). No statistically significant difference was observed with the reference versus biosimilar trastuzumab for PFS (median PFS, 6.9 vs. 5.4 mo; P =0.98) or OS (median OS, 12.3 mo vs. not reached; P =0.42). Safety profiles were similar between the 2 groups. Conclusions: Biosimilar trastuzumab showed equivalent outcome to reference trastuzumab, with similar adverse events. Biosimilar trastuzumab can suitably and safely replace trastuzumab as a reference for the treatment of HER2-positive AGC.

Objectives: Trastuzumab is used as an agent against human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer (AGC). The aim of this study was to determine how HER2 gene amplification and neutrophil-to-lymphocyte ratio (NLR) could predict long-term survival in AGC patients that underwent trastuzumab-based chemotherapy.Methods: We retrospectively reviewed medical records of 112 patients between 28 and 91 years old (median of 66 y) with AGC treated with first-line trastuzumab-based chemotherapy. The level of HER2 gene amplification was determined by the HER2/centromere enumerator probe 17 (CEP17) ratio and HER2 gene copy number (GCN). NLR was calculated as the neutrophil count divided by the lymphocyte counts.Results: Median HER2/CEP17 ratio, HER2 GCN, and NLR values were 2.85, 7.1, and 2.81, respectively. Objective response rate in both high HER2/CEP17 ratio (59.4% vs. 28.1%, P = 0.012) and HER2 GCN groups (62.1% vs. 33.3%, P = 0.032) was higher than that of each group. High NLR correlated with significantly worse median overall survival (OS) (median OS, 8.2 vs. 18.9 mo, P = 0.002) and progression free survival (PFS) (median PFS: 5.1 vs. 8.0 mo, P = 0.005). However, median OS and PFS were not significantly different according to HER2/ CEP17 ratio or HER2 GCN. In the multivariate analysis, high NLR, Eastern Cooperative Group performance status, and poorly differentiated/signet ring cell type were independent factors for OS.Conclusions: NLR was a significant predictor of long-term survival in AGC patients treated with first-line trastuzumab-based chemotherapy. Future validation of prospective trials with larger patient populations will be needed.

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e22011 Background: There was few data for molecular characteristics of Asian metastatic melanoma patients with distinct clinical features as compared to West patients with metastatic melanoma. We conducted the molecular profiling for Asian metastatic melanoma patients with check-point inhibitors (CPIs) to find novel biomarkers to CPIs. Methods: 164 Asian patients with metastatic melanoma who received CPIs were simultaneously tested by the next generation sequencing (NGS) in tumor samples. We collected all NGS data and clinic-pathologic factors and also analyzed biomarkers for tumor response to CPIs. Results: The most common subtype was acral melanoma (39.6%) followed by cutaneous melanoma (32.3%), mucosal melanoma (26.2%) and others (1.8%). 163 pts are evaluable for efficacy; we observed 40 complete response (24.4 %), 34 confirmed partial responses (20.7%), 41 stable disease (25.0%) and 48 disease progression (29.3%). The overall confirmed response rate from the dose escalation is 45.1%. There was no significant difference of tumor response among subtypes of melanoma (p = 0.295). NRAS and TP53 mutation and NF2 deletion were significantly related to patients without the response to CPIs (p < 0.05). Meanwhile, MYC and RPS6KB1 amplification were found with those with the response (p < 0.05). The median progression free survival (PFS) to ICIS was 5.9 months (95% CI 3.8 - 8.05 months). Univariate analysis showed that TP53 and BRAF mutation, NF2 deletion, and BIRC2 amplification were poor prognostic values for PFS (p < 0.05). Conclusions: This study reported molecular characteristics of 164 Asian patients with metastatic melanoma. The specific molecular alterations influenced on the tumor response and PFS to CPIs in those.