Survival of Patients with Metastatic HER2 Positive Gastro-Oesophageal Cancer Treated with Second-Line Chemotherapy Plus Trastuzumab or Ramucirumab after Progression on Front-Line Chemotherapy Plus Trastuzumab

69 Background: Optimal second line treatment for patients with metastatic HER2 positive gastroesophageal cancer (Her2GE) is unknown. A retrospective study has suggested continuation of chemotherapy with trastuzumab (CT), as compared to chemotherapy alone, may improve outcomes. However, CT has never been compared to the current standard second-line treatment of chemotherapy plus ramucirumab (CR). Methods: The Flatiron Health EHR-derived database, a nationally representative database comprising patient-level structured and unstructured data, curated via technology-enabled abstraction, was reviewed for patients with metastatic Her2GE who received CT in the first line setting, followed by either second line CT or CR. Survival from second line therapy (SST) and time to next therapy or death (TTNTD) were compared using Kaplan-Meier curves and Log-Rank analysis. Demographics between treatment groups were compared using standard T tests and chi-squared analysis. Results: 135 patients were identified, of whom 34 received second-line CR and 101 received CT. Median SST for patients treated with CT was 10.2 months (m) [interquartile range (IQR) 5.1-20.8] and 6.8 m (IQR 3.2-20.2) for those treated with CR, p = 0.39. Median TTNTD for patients treated with CT versus CR was 4.9 m (IQR 2.8-9.8) and 4.8 m (IQR 2.3-7.5), respectively (p = 0.53). There was no difference between patients who received CT or CR in regards to average age (63 vs. 62, p = 0.72), average duration of first-line therapy (7.8 m vs. 9.1 m, p = 0.36), or percentage of patients with ECOG > 1 (15% vs. 22%, p = 0.50). Patients who received CT were more likely to receive a multiagent chemotherapy backbone (76% vs. 3%, p ≤ 0.001). Conclusions: This data suggest a non-significant trend towards increased SST for patients treated with second line CT versus CR. Further studies are needed to clarify optimal second-line treatment for this patient population.