LAUSR

e16037 Background: Apatinib, a highly selective VEGFR2 inhibitor, has shown a clinical benefit as third-line or further-line treatment in patients with gastric cancer in a randomized phase III study with the initial dose of 850mg. However, the study was conducted in a small scale (n = 267) under standardized conditions. Here, we assessed exposure and effectiveness of apatinib at different doses using data collected from a post-marketing phase IV study that included a broader patient population with a larger sample size. Methods: Patients with advanced or metastatic advanced gastric cancer or gastroesophageal junction adenocarcinoma who were aged 18-75 with ECOG performance status of 0-2 and failed at least two lines of chemotherapy were enrolled. Apatinib was recommended with an initial dose of 850 mg q.d orally, while the initial dose was determined at the discretion of the investigators. Administration of apatinib regarding the initial dose, duration of treatment, dose modification, average daily exposure dose (ADED) and its effect on progression-free survival (PFS) and overall survival (OS) were analyzed. Results: A total of 2004 patients were included in the intention-to-treat population. The median age was 59 (range, 19-85) years, 71.8% of patients were male, 84.2% had ECOG performance status of 0-1; 96.4% had stage IV disease, and 98.8% had metastases, among which 34.2% with more than 2 metastases. Five patients did not receive therapy. Compared to 5.5% of patients with the initial dose > 500mg, 94.1% was given at the initial dose≤500mg; 8.6% had ADED > 500mg and 91.1% had ADED ≤500mg. The median duration of treatment was 56 days. Treatment interruption and discontinuation, and dose reduction occurred in 34.4%, 24.5%, and 13.7% of patients due to adverse events, respectively. Survival analyses in the initial dose ≤500mg/ > 500mg subgroups showed median PFS of 2.6 months (95%CI 2.20-2.79) vs 2.7 months (95% CI 1.91-3.32), median OS of 5.6 months (95% CI 5.26-5.95) vs 5.9 months (95% CI 4.40-6.87). In the ADED ≤500mg/ > 500mg subgroups, the median PFS was 2.6 months (95% CI 2.14-2.76) vs 3.0 months (95% CI 2.27-3.61), and median OS was 5.7 months (95% CI 5.32-6.08) vs 6.1 months (95% CI 5.36-7.72). Conclusions: In conclusion, more than 90% of the patients received a lower dose regimen, which indicate dosage of 500mg or lower is a tolerated exposure. Furthermore, dose at 500mg or lower produced similar efficacy to that more than 500mg. Clinical trial information: NCT02426034.