Overview

Gastric cancer 90-gene testing extends the genomic workup of advanced disease with a broader panel spanning targeted-therapy, chemotherapy, and MSI/MMR markers. Rather than testing every patient identically, the panel is most informative when applied to biomarker-selected populations in whom a specific result is likely to change management. This article outlines the subgroups that gain the most from comprehensive profiling, and why indiscriminate use can waste both tissue and budget. Because tissue from gastric cancer is often limited, reserving the broad panel for cases where the result can genuinely redirect therapy respects both the sample and the patient's time, and prevents the report from becoming a static document nobody acts on.

HER2-Positive and CLDN18.2 Populations

Human epidermal growth factor receptor 2-positive gastric cancer remains a defined population for anti-HER2 therapy, and confirmatory testing is standard of care. Claudin 18.2 expression defines another molecularly selected group under active targeted development. A 90-gene panel places these markers in context with coexisting alterations, helping teams understand whether a single pathway or several are driving the tumor and whether combination targeting is worth considering.

Microsatellite-Instable and PD-L1-High Disease

Patients with microsatellite-instable or mismatch-repair-deficient tumors may be candidates for immune checkpoint inhibition per approved labeling, independent of tumor site. Elevated PD-L1 expression further identifies populations studied for immunotherapy combinations. Including MSI/MMR and PD-L1-associated context in one report streamlines the route to biomarker-driven treatment and avoids ordering separate assays sequentially.

Selectively Applying Broad Panels

Broad panels are best reserved for advanced or treatment-refractory cases where the result can redirect therapy or enrollment. In early-stage disease, narrower validated assays may be preferential because the clinical question is already well defined. Choosing the right population protects both budgets and tissue, and ensures the 90-gene report answers a question the care team actually faces rather than generating unused data.

FAQ

Q: Should every gastric cancer patient receive a 90-gene panel? A: Not necessarily. Broad profiling is most useful in advanced or refractory disease where the result can change therapy or trial access.

Q: Which populations benefit most from MSI/MMR testing? A: Microsatellite-instable or mismatch-repair-deficient tumors may qualify for immune checkpoint therapy under labeling, regardless of anatomical stage.

Q: How does the panel support CLDN18.2 decisions? A: It places CLDN18.2 and other alterations in a broader genomic context, showing whether additional targetable pathways coexist.