KEYNOTE-522
The trial that added immunotherapy to pre-surgery chemotherapy for triple-negative breast cancer and, uniquely, improved survival.
1,174 patients. pCR 64.8% vs 51.2%; event-free survival at 5 years 81.2% vs 72.2%; 7-year EFS 78.3% vs 69.8% and OS 85.1% vs 77.2% (ASCO 2026 update). Defines the standard of care for stage II-III TNBC. Open questions: whether adjuvant pembrolizumab is needed after pCR (OptimICE-pCR) and how to escalate for residual disease.
Setting
Early-stage (II-III) TNBC: pembrolizumab + chemotherapy before surgery, pembrolizumab after
Phase
Phase 3
Sponsor
Merck
Registry
Headline result
EFS HR 0.63; OS HR 0.66 (5-year); 7-year OS 85.1% vs 77.2%.
Reported
2020
Enrolled
1174
Replication
Single pivotal trial, but the EFS and OS benefits held through the 5- and 7-year analyses; consistent with IMpassion031 (atezolizumab, pCR only) and with real-world neoadjuvant pembrolizumab series.
In plain words
What these results mean for people, not percentages
Pathologic complete response (ypT0/Tis ypN0)primarysurrogate endpoint
- 64.8 vs 51.2 out of 100 had no cancer left at surgery with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; 13.6 more per 100.
- Roughly one extra person helped for every 7 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- The p-value (0.00055) says a difference this large would rarely happen by chance; it does not say how large or how useful the difference is.
- 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.
Event-free survival at 5 yearsprimarysurrogate endpoint
- 81.2 vs 72.2 out of 100 free of a major event at 5 years with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; 9 more per 100.
- Roughly one extra person helped for every 11 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- Put another way, the treated group had about 35 percent lower chance of the event at any given time (hazard ratio 0.65, likely range 0.51 to 0.83).
- 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 survival at 5 yearssurvival endpoint
- 86.6 vs 81.7 out of 100 alive at 5 years with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; 4.9 more per 100.
- Roughly one extra person helped for every 20 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- Put another way, the treated group had about 34 percent lower chance of the event at any given time (hazard ratio 0.66, likely range 0.5 to 0.87).
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
Event-free survival at 7 yearssurrogate endpoint
- 78.3 vs 69.8 out of 100 free of a major event at 7 years with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; 8.5 more per 100.
- Roughly one extra person helped for every 12 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.
Overall survival at 7 yearssurvival endpoint
- 85.1 vs 77.2 out of 100 alive at 7 years with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; 7.9 more per 100.
- Roughly one extra person helped for every 13 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
Be careful
- These results apply to the people the trial enrolled: Early-stage (II-III) TNBC: pembrolizumab + chemotherapy before surgery, pembrolizumab after. 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.
1,174 participants enrolled.
Pathologic complete response (ypT0/Tis ypN0)primary
· p = 0.00055
Pembrolizumab + chemotherapy64.8 of 100
n = 401
Placebo + chemotherapy51.2 of 100
n = 201
Event-free survival at 5 yearsprimary
HR 0.65 (0.51–0.83)
Pembrolizumab + chemotherapy81.2 of 100
n = 784
Placebo + chemotherapy72.2 of 100
n = 390
Overall survival at 5 years
HR 0.66 (0.5–0.87) · p = 0.002
Pembrolizumab + chemotherapy86.6 of 100
Placebo + chemotherapy81.7 of 100
Event-free survival at 7 years
Pembrolizumab + chemotherapy78.3 of 100
Placebo + chemotherapy69.8 of 100
Overall survival at 7 years
Pembrolizumab + chemotherapy85.1 of 100
Placebo + chemotherapy77.2 of 100
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Pathologic complete response (ypT0/Tis ypN0)primary | Pembrolizumab + chemotherapy | 401 | 64.8% | — | 0.00055 | link |
| Placebo + chemotherapy | 201 | 51.2% | ||||
| Event-free survival at 5 yearsprimary | Pembrolizumab + chemotherapy | 784 | 81.2% | 0.65 (0.51–0.83) | — | link |
| Placebo + chemotherapy | 390 | 72.2% | ||||
| Overall survival at 5 years | Pembrolizumab + chemotherapy | — | 86.6% | 0.66 (0.5–0.87) | 0.002 | link |
| Placebo + chemotherapy | — | 81.7% | ||||
| Event-free survival at 7 years | Pembrolizumab + chemotherapy | — | 78.3% | — | — | link |
| Placebo + chemotherapy | — | 69.8% | ||||
| Overall survival at 7 years | Pembrolizumab + chemotherapy | — | 85.1% | — | — | link |
| Placebo + chemotherapy | — | 77.2% |
Replication
Single pivotal trial, but the EFS and OS benefits held through the 5- and 7-year analyses; consistent with IMpassion031 (atezolizumab, pCR only) and with real-world neoadjuvant pembrolizumab series.