Overview

Gastric cancer 70-gene testing is a targeted-plus-chemotherapy plus MSI/MMR next-generation sequencing panel designed to map the molecular landscape of an individual tumor. Its real value emerges when the panel is combined with companion diagnostics rather than read in isolation. This article explains how laboratories and oncology teams integrate a 70-gene report with orthogonal assays to guide therapy decisions, turning a long variant list into a treatment plan the care team can trust. In routine practice the combined workflow cuts the number of separate assays a patient must undergo and gives the molecular tumor board one coordinated evidence base to debate, which shortens the path from biopsy to a reasoned therapy choice.

Why Combine NGS With IHC and FISH

NGS excels at detecting sequence alterations across many genes at once, but protein-level confirmation remains valuable. Human epidermal growth factor receptor 2 status, for example, is conventionally assessed by immunohistochemistry and in situ hybridization, and a 70-gene panel complements rather than replaces that workflow. Combining methods reduces the risk of a false-negative call that could withhold an appropriate targeted option, and it resolves ambiguous single-assay results through orthogonal evidence.

Matching Results to Targeted and Chemotherapy Choices

The panel reports alterations linked to targeted agents and markers associated with chemotherapy sensitivity, plus MSI/MMR status. A microsatellite-instable or mismatch-repair-deficient result can indicate eligibility for immune checkpoint inhibition per labeling, while other alterations point toward clinical trial options. Presenting the NGS result alongside a clear companion-diagnostic summary helps treating physicians move from data to a concrete regimen with documented rationale.

Building a Combined Reporting Workflow

A practical workflow pairs the sequencing report with a structured companion section: confirmed IHC/FISH results, MSI/MMR call, and a curated list of alterations with therapy or trial associations. Laboratories should standardize turnaround and clearly flag variants of unknown significance so clinicians are not misled. Such integration turns a standalone gene list into an actionable treatment map and shortens the path from biopsy to informed therapy selection.

FAQ

Q: Does a 70-gene panel replace HER2 testing by IHC? A: No. Protein-level HER2 assessment by IHC and in situ hybridization remains the standard; the panel complements it by adding genomic context.

Q: What does MSI/MMR status add clinically? A: MSI-H or dMMR results can indicate eligibility for immune checkpoint therapy under approved labeling and are part of standard gastric workup.

Q: How should variants of unknown significance be handled? A: They should be reported transparently and not used alone to select therapy; confirmation and clinical correlation are required.