MATTERHORN
Adding immunotherapy before and after surgery cut deaths in early stomach cancer; nearly seven in ten patients were alive at three years.
EFS HR 0.71; pCR 19.2% vs 7.2%; OS HR 0.78 (3-year OS 68.6% vs 61.9%, ESMO 2025). FDA approval 25 November 2025, the first perioperative immunotherapy in gastric cancer. Benefit was consistent across PD-L1 levels; the trial did not include a chemotherapy-free arm.
Setting
Resectable stage II-IVA gastric/GEJ adenocarcinoma: perioperative FLOT + durvalumab vs FLOT + placebo
Phase
Phase 3
Sponsor
AstraZeneca
Registry
Headline result
EFS HR 0.71; OS HR 0.78; 3-year OS 68.6%.
Reported
2025
Enrolled
948
Replication
KEYNOTE-585 (pembrolizumab + chemotherapy) improved pCR but not EFS significantly; MATTERHORN is the only positive perioperative IO trial so far.
In plain words
What these results mean for people, not percentages
Event-free survivalprimarysurrogate endpoint
- The treated group had about 29 percent lower chance of the event at any given time (hazard ratio 0.71).
- The absolute difference, how many more people out of 100 were helped, is not reported here.
- This is a surrogate endpoint: it measures the cancer being controlled or absent on scans and tests, which often, but not always, translates into living longer.
Overall survivalsurvival endpoint
- The treated group had about 22 percent lower chance of the event at any given time (hazard ratio 0.78).
- The absolute difference, how many more people out of 100 were helped, is not reported here.
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
Pathologic complete responsesurrogate endpoint
- 19.2 vs 7.2 out of 100 had no cancer left at surgery with FLOT + durvalumab compared with FLOT + placebo; 12 more per 100.
- Roughly one extra person helped for every 8 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- This is a surrogate endpoint: it measures the cancer being controlled or absent on scans and tests, which often, but not always, translates into living longer.
Be careful
- These results apply to the people the trial enrolled: Resectable stage II-IVA gastric/GEJ adenocarcinoma: perioperative FLOT + durvalumab vs FLOT + placebo. People in a different situation may not see the same effect.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
948 participants enrolled.
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Event-free survivalprimary | FLOT + durvalumab | 474 | — | 0.71 | — | link |
| FLOT + placebo | 474 | — | ||||
| Overall survival | FLOT + durvalumab | 474 | — | 0.78 (0.63–0.96) | 0.021 | link |
| FLOT + placebo | 474 | — | ||||
| Pathologic complete response | FLOT + durvalumab | — | 19.2 percent | — | — | link |
| FLOT + placebo | — | 7.2 percent |
Replication
KEYNOTE-585 (pembrolizumab + chemotherapy) improved pCR but not EFS significantly; MATTERHORN is the only positive perioperative IO trial so far.