ASCO GI 2026 | Comprehensive biomarker testing and heterogeneity in gastric cancer

Already, we need to test multiple biomarkers in front-line, including MSI, PD-L1, HER2, and CLDN18.2. And this kind of biomarkers should be also important in later-line, more and more in the near future. So we have a HER2 testing as a standard of care, particularly for HER2-positive disease. So to test HER2-positive status after a first-line chemo trastuzumab or upcoming chemo trastuzumab combination should be still important. And we are waiting for additional phase 3 study or other study using HER2-targeted agent like ADC. And it also based on HER2 status after pertuzumab. And sometimes we see the reduced loss of HER2 status and increased HER2 expression in the same patient. So this kind of temporal heterogeneity of a biomarker should be very important in gastric cancer, even in later-line setting. So that means before considering sequence of new types of treatment, always we need to test biomarker just before a new treatment. But always, biomarker is not always feasible. For example, if a patient has a distant metastasis, so we need to have a multidisciplinary team of management to consider a needle biopsy from distant metastasis or sometimes a surgical approach like laparoscopy. And for future, maybe we have a more sophisticated technique like imaging technology because HER2 is a protein, so we can use such kind of imaging like PET scan. So eventually it may be more convenient and less invasive for patients. I believe such technology advances also very important to cause the sequence of treatment in the near future.

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