Treatment of Microsatellite Instability-High (MSI-H) Gastric Cancer in the Curative Surgery Setting

Microsatellite instability-high (MSI-H) status defines a distinct molecular subgroup of gastric cancer with specific management implications when curative-intent surgery is planned or has been performed.

This protocol applies to patients with confirmed MSI-H gastric cancer being managed in the curative (radical) surgery setting. MSI-H status materially alters the recommended approach to both perioperative and adjuvant treatment compared with non-MSI-H disease.

Treatment Approach

Radical surgical resection remains the cornerstone of management in this setting. The role of post-operative chemotherapy in MSI-H resected gastric cancer differs from standard practice. If tumour downstaging is required before surgery, a specific multi-agent chemotherapy combination is recommended. The complete regimen details, sequencing, and decision criteria are available via the link below.

Instant Access to Structured Evidence-Based Regimens

References

DOI: 10.1016/j.annonc.2022.07.004

For patients with MSI-H gastric cancer who have undergone curative surgery, adjuvant ChT cannot be recommended [IV, D], but if a response is required to downstage a tumour before surgery, FLOT is recommended.
Although evidence is limited, adjuvant (post-operative) ChT should be avoided in resected MSI-H gastric cancers.
Therefore, if a response is required to downstage an MSI-H tumour before surgery, FLOT is recommended.

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