KEYNOTE-177
The trial that made immunotherapy alone, with no chemotherapy, the first treatment for the 5% of bowel cancers with a broken DNA spell-checker. Over half of patients were alive at five years.
Pembrolizumab doubled median PFS (16.5 vs 8.2 months, HR 0.60) and at 5-year follow-up (Annals of Oncology 2024) median OS was 77.5 months with a 5-year OS of 54.8%, despite 62% of chemotherapy patients crossing over to anti-PD-1 therapy. First-line FDA approval June 2020. ESMO-MCBS grade 4. The comparator arm's crossover means the OS hazard ratio (0.73) understates the benefit.
- Median 16.5 vs 8.2 months with Pembrolizumab compared with Chemotherapy; about 8.3 months longer for half the group.
- A median is a midpoint: half the people did better than this and half did worse, so it is not a prediction for any one person.
- Put another way, the treated group had about 40 percent lower chance of the event at any given time (hazard ratio 0.6, likely range 0.45 to 0.8).
- 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.
- Median 77.5 vs 36.7 months with Pembrolizumab compared with Chemotherapy; about 40.8 months longer for half the group.
- A median is a midpoint: half the people did better than this and half did worse, so it is not a prediction for any one person.
- Put another way, the treated group had about 27 percent lower chance of the event at any given time (hazard ratio 0.73).
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
- These results apply to the people the trial enrolled: First-line MSI-H/dMMR metastatic colorectal cancer: pembrolizumab vs investigator-choice chemotherapy. People in a different situation may not see the same effect.
- The trial selected people by a biomarker (MSI-H); the result should not be assumed for people whose cancer does not have it.
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.
307 participants enrolled.
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Progression-free survivalprimary | Pembrolizumab | 153 | 16.5 months | 0.6 (0.45–0.8) | — | link |
| Chemotherapy | 154 | 8.2 months | ||||
| Overall survival (5-year follow-up) | Pembrolizumab | 153 | 77.5 months | 0.73 | — | link |
| Chemotherapy | 154 | 36.7 months |