[HER2 testing and targeted therapy in advanced gastric cancer]

A large phase III study on the use of the HER2 antibody trastuzumab in locally advanced or metastatic gastric cancer has now been completed. Patients whose tumors were either scored on immunohistochemistry (IHC) as 3+ (independently of the result of fluorescence in situ hybridization (FISH)) or as IHC2+ and FISH+ were found, in a planned subgroup analysis, to have a median overall survival time of 16.0 months--versus 11.8 months when trastuzumab was not given. In light of these data, trastuzumab was therefore approved by the European Medicines Agency (EMEA) for metastasizing patients with this HER2 test result. It should be noted that the IHC scoring system for gastric cancer was modified compared to that for breast cancer. If the same criteria as are used for breast cancer were used for gastric cancer, this would lead to a large number of false negatives; around half of the patients who would benefit from trastuzumab would not be identified. Workshops for pathologists and round robin tests are being carried out to introduce the new scoring system.