Addition of trastuzumab to perioperative chemotherapy in HER2-positive gastroesophageal adenocarcinoma patients: A multicenter retrospective observational AGEO study

Approximately 10-20% of patients with gastroesophageal adenocarcinoma (GE-ADK) have HER2-positive tumors. The addition of trastuzumab to chemotherapy improves OS in patients with advanced disease. We investigated the effect of perioperative trastuzumab on survival outcomes.This French, multicenter, retrospective observational study included HER2-positive GE-ADK patients treated between January 2015 and December 2020. The primary endpoint was DFS at 18 months. Secondary endpoints were pathological complete response rate (pCR), R0 resection rate, OS, and toxicity.Forty-eight patients were included, and they received a median of 6 cycles of preoperative treatment, with grade III/IV adverse events occurring in 23%. Pathologic complete response (pCR) and major pCR according to Mandard system were achieved in 5/48 (10%) and 20/48 (42%) patients, respectively. Loss of HER2 expression was observed in 18/48 (38%) patients. Postoperative complications rate according to the Clavien Dindo classification (≥3) was 37.5%. After a median follow-up of 29 months, the 18-month DFS was 80.4% (95% CI 68.9-93.8) and the 2-year OS rate was 89.0%. Subgroup analysis showed a longer DFS for gastric tumor than gastro-esophageal junction tumor.This study suggests that perioperative chemotherapy with trastuzumab in patients with HER2-positive GE-ADK is feasible and safe with encouraging survival.