Real-World Data of Trastuzumab Deruxtecan for Advanced Gastric Cancer: A Multi-Institutional Retrospective Study.

Trastuzumab deruxtecan (T-DXd) has shown promising efficacy against HER2-positive advanced gastric cancer (AGC). However, data on its real-world efficacy in AGC patients are insufficient, and the predictive marker of T-DXd is unclear. In this multi-center retrospective study, we collected clinical information of 18 patients with HER2-positive AGC who received T-DXd after intolerant or refractory responses to at least two prior regimens and analyzed predictive factors. The median age was 71 years (range: 51-85), 13 men were included, and ECOG performance status (PS): 0/1/2/3 was 9/6/2/1. A total of 11 patients (61%) received prior immune checkpoint inhibitors (ICIs), 14 patients were HER2 3+, and 4 patients were HER2 2+/FISH positive. The median trastuzumab (Tmab)-free interval was 7.7 months (range: 2.8-28.6). The overall response rate was 41%, and the disease control rate was 76%. Median progression-free survival (PFS) was 3.9 months (95% CI: 2.6-6.5), and median overall survival (OS) was 6.1 months (95% CI: 3.7-9.4). PFS (6.5 vs. 2.9 months, p = 0.0292) and OS (9.2 vs. 3.7 months, p = 0.0819) were longer in patients who received prior ICIs than in those who had not. PFS (6.5 vs. 3.4 months, p = 0.0249) and OS (9.4 vs. 5.7 months, p = 0.0426) were longer in patients with an 8 month or longer Tmab-free interval. In patients with ascites, PFS (6.5 vs. 2.75 months, p = 0.0139) and OS (9.4 vs. 3.9 months, p = 0.0460) were shorter. T-DXd showed promising efficacy in HER2-positive AGC patients in a real-world setting. Pre-administration of ICIs and a sufficient Tmab-free interval may be predictive factors of T-DXd efficacy.