Individual patient data meta-analysis of microsatellite instability as a biomarker in gastric cancer (MAGIC, CLASSIC, ARTIST, ITACA-S)
Pooling four trials showed that microsatellite-unstable gastric cancers have a much better prognosis after surgery and gain nothing from perioperative or adjuvant chemotherapy, which may even harm them.
Overview
Individual patient data meta-analysis of 1,556 patients from four randomised trials of resectable gastric cancer (MAGIC, CLASSIC, ARTIST, ITACA-S), of whom 7.8 percent had microsatellite instability-high tumours.
Five-year disease-free survival was 71.8 versus 52.3 percent and overall survival 77.5 versus 59.3 percent for microsatellite-unstable versus stable tumours; chemotherapy improved survival in stable tumours (hazard ratio 0.65) but not in unstable ones (hazard ratio 1.03), with a suggestion of harm.
- Five-year overall survival 77.5 percent (unstable) vs 59.3 percent (stable) with surgery alone.
- Chemotherapy hazard ratio 1.03 in microsatellite-unstable tumours vs 0.65 in stable.
Microsatellite instability testing is recommended before perioperative chemotherapy for gastric cancer, and immunotherapy-based trials are the preferred approach for unstable tumours.
- Small number of microsatellite-unstable patients (121); confidence intervals were wide.