Impact of deviations in HER2 expression test results on survival in metastatic gastric cancer

The multicenter prospective VARIANZ study in Germany found significant discrepancies in HER2 assessment of metastatic gastric cancer, resulting in poor overall survival of trastuzumab treated patients with tumors that were locally tested as HER2-positive but in central testing appeared to be HER2-negative. The authors conclude that borderline HER2 positivity and heterogeneity of HER2 expression should be considered resistance factors for HER2-targeting treatment of mGC.