Increased assessment of HER2 in metastatic gastroesophageal cancer patients: a nationwide population-based cohort study

Background Addition of trastuzumab to first-line palliative chemotherapy in gastroesophageal cancer patients with HER2 overexpression has shown to improve survival. Real-world data on HER2 assessment and administration of trastuzumab are lacking. The aim of this study was to assess HER2 testing, trastuzumab administration, and overall survival (OS) in a nationwide cohort of metastatic gastroesophageal cancer patients. Methods Data of patients with synchronous metastatic gastroesophageal adenocarcinoma diagnosed in 2010–2016 that received palliative systemic treatment ( n = 2846) were collected from the Netherlands Cancer Registry and Dutch Pathology Registry. The ToGA trial criteria were used to determine HER2 overexpression. Proportions of HER2 tested patients were analyzed between hospital volume categories using Chi-square tests, and over time using trend analysis. OS was tested using the Kaplan Meier method with log rank test. Results HER2 assessment increased annually, from 18% in 2010 to 88% in 2016 ( P