Real-world effectiveness and safety of trastuzumab-deruxtecan in Japanese patients with HER2-positive advanced gastric cancer (EN-DEAVOR study)

Background Trastuzumab-deruxtecan (T-DXd) was approved for the treatment of HER2-positive patients with advanced gastric cancer in Japan based on the results of the DESTINY-Gastric01 trial. This study aimed to collect real-world data and evaluate the effectiveness and safety of T-DXd. Methods Patients aged >= 20 years at the start of T-DXd administration with a histopathologically confirmed diagnosis of HER2-positive unresectable advanced or recurrent gastric or gastroesophageal junction (GEJ) adenocarcinoma that had worsened after chemotherapy were enrolled in this retrospective cohort study. Key outcomes included T-DXd treatment status, overall survival (OS), real-world progression-free survival (rwPFS), time to treatment failure (TTF), objective response rate and frequency of grade >= 3 adverse events (AEs). Results Of the 312 patients included in the analysis, 75.3% were male, the median (range) age was 70.0 (27.0-89.0) years, 12.2% had an ECOG PS >= 2, 43.3% had ascites and the initial T-DXd dose was > 5.4- <= 6.4 mg/kg in 78.2% of patients. The median (95% confidence interval) OS, rwPFS and TTF (months) was 8.9 (8.0-11.0), 4.6 (4.0-5.1) and 3.9 (3.4-4.2), respectively. The response rate was 42.9% in patients with a target lesion. In total, 48.4% of patients experienced a grade >= 3 AE, 2.6% experienced grade 5 AEs and 60.9% experienced AEs leading to T-DXd dose adjustments (reduction: 36.9%, interruption: 34.0% or discontinuation: 23.7%). No new safety signals were detected. Conclusions T-DXd was effective and had a manageable safety profile as a third- or later-line treatment for patients with HER2-positive gastric or GEJ cancer in Japanese clinical practice.