Prioritizing Biomarker Testing to Conserve Tissue in Gastroesophageal Cancer

In an interview with CancerNetwork®, Rutika Mehta, MD, MPH, director of Upper Gastrointestinal (GI) Medical Oncology at NYU Langone Health’s Perlmutter Cancer Center, discussed how academic and community practices can streamline biomarker workflows so that treatment decisions for patients with gastroesophageal cancer are not delayed.

Mehta noted that limited tissue is a shared challenge in both settings, as samples collected from the initial endoscopy or a metastatic site are often small. To conserve tissue, she obtains microsatellite instability (MSI) and mismatch repair status through liquid biopsy and then prioritizes immunohistochemistry for HER2, claudin 18.2, and PD-L1, in that order. When tissue is not scarce, she explained, all 4 biomarkers can typically be assessed by immunohistochemistry. This approach is intended to preserve material for testing that directly informs first-line treatment selection and clinical trial eligibility, while still allowing clinicians to move quickly toward a treatment decision.

Transcript:

Mehta: That’s a very critical question. One of the major criticisms we always face as academicians from community physicians is that, yes, it’s great to have different biomarker testing done and available to guide treatment decisions and to help patients be offered clinical trials. The truth of the matter is, be it community practice or academic settings, tissue becomes an issue. The amount of tissue that has been collected from either the initial endoscopy or from a metastatic site is typically quite limited.

I try to prioritize. I typically find out whether a tumor is mismatch repair deficient or microsatellite instability–high [MSI-H] through a liquid biopsy, so MSI is the last test I would use tissue for. I typically get MSI testing through liquid biopsy, and then I try to prioritize HER2, claudin 18.2, and then PD-L1, in that order. That way, I can save some tissue. If there is no scarcity of tissue, then we can typically do all 4 of those on immunohistochemistry.