1586P Characteristics, treatment (Tx) patterns and outcomes of patients with advanced/metastatic gastric cancer (GC) or gastro-esophageal junction (GEJ) adenocarcinoma previously treated with anti-HER2 therapy in an English national registry

Understanding the natural history of patients with GC/GEJ adenocarcinoma treated previously with anti-HER2 regimens is useful for understanding the disease burden and selecting the optimal Tx for this population. This study reports Tx patterns and outcomes of patients with GC/GEJ adenocarcinoma treated previously with anti-HER2-based regimens. Adults with advanced/metastatic GC/GEJ adenocarcinoma who received first-line (1L) trastuzumab-containing regimens were identified in the English Cancer Outcomes and Services Dataset (Jan 2010–Dec 2019). Tx pathways and outcomes were obtained from the Systemic Anti-Cancer Therapy Dataset, which captured nearly all treatments in England. A novel regimen-based algorithm for reporting Tx sequencing and outcomes was developed since line of therapy was not in the database. Descriptive statistics were reported. Overall survival (OS) and time to Tx discontinuation or death (TTD) underwent Kaplan–Meier analysis. A total of 948 patients were identified. At the start of their 1L trastuzumab-containing Tx, median age was 67 years (interquartile range [IQR] 57–73]); 82.1% were male; 90.4% were White; 85.4% had an ECOG status of 0–1; 26.0% had liver metastases; 1.0% had brain metastases; and 81.2% had a Charlson Comorbidity Index of 0–1. Three hundred and sixteen patients (33.3%) received 2L onward; 63 (6.6%) received 3L onward. The most common 2L regimens were paclitaxel (n=115 [36.4%]), docetaxel (n=98 [31.0%]), and 5-fluorouracil (5FU) + irinotecan (n=19 [6.0%]). Common 3L regimens included 5FU + irinotecan (n=12 [19.1%]), paclitaxel (n=11 [17.5%]) and capecitabine + irinotecan (n=10 [15.9%]). Median TTD was 2.8 months from the start of 2L. Median OS was 6.1 months (IQR, 3.4–11.2) from the start of 2L and 5.9 months (IQR, 3.2–9.5) from the start of 3L. Survival of patients with GC/GEJ adenocarcinoma previously treated with 1L anti-HER2 regimens remains poor after 2L and 3L therapy, which is limited mainly to chemotherapy. These findings reflect an urgent need to improve 2L and 3L options.