Extra-gain of HER2-positive cases through HER2 reassessment in primary and metastatic sites in advanced gastric cancer with initially HER2-negative primary tumours: Results of GASTric cancer HER2 reassessment study 1 (GASTHER1)

Repeat HER2 assessment in primary and metastatic or recurrent sites is recommended in patients with advanced gastric cancer whose primary tumour is initially HER2-negative.