OnCo
trialsTrialPositive

KEYNOTE-355

Established immunotherapy plus chemotherapy as first-line treatment for metastatic triple-negative breast cancer with PD-L1 expression.

OS 23.0 vs 16.1 months in PD-L1 CPS ≥10 (HR 0.73). No benefit in CPS <10, defining the PD-L1 threshold used today. Now being succeeded by ADC-based first-line regimens (ASCENT-04).

Setting
First-line metastatic TNBC: pembrolizumab + chemotherapy vs chemotherapy
Phase
Phase 3
Sponsor
Merck
Registry
NCT02819518
Headline result
OS HR 0.73 in CPS ≥10.
Reported
2020
Enrolled
847
Replication
Consistent direction with IMpassion130 (atezolizumab, PD-L1+); IMpassion131 was negative, so the PD-L1 CPS ≥10 population and the chemotherapy partner matter. Now being superseded by ADC + pembrolizumab (ASCENT-04).

Outcomes

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In plain words
What these results mean for people, not percentages
847 people took part
Overall survival, PD-L1 CPS ≥10primarysurvival endpoint
  • Median 23 vs 16.1 months with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; about 6.9 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, likely range 0.55 to 0.95).
  • Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
Progression-free survival, PD-L1 CPS ≥10primarysurrogate endpoint
  • Median 9.7 vs 5.6 months with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; about 4.1 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 34 percent lower chance of the event at any given time (hazard ratio 0.66, likely range 0.5 to 0.88).
  • 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, CPS ≥1survival endpoint
  • Median 17.6 vs 16 months with Pembrolizumab + chemotherapy compared with Placebo + chemotherapy; about 1.6 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 14 percent lower chance of the event at any given time (hazard ratio 0.86, likely range 0.72 to 1.04).
  • The likely range for the hazard ratio crosses 1, so the difference could be due to chance.
  • Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
  • Not significant.
Be careful
  • These results apply to the people the trial enrolled: First-line metastatic TNBC: pembrolizumab + chemotherapy vs chemotherapy. 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.

847 participants enrolled.

Overall survival, PD-L1 CPS ≥10primary
HR 0.73 (0.55–0.95) · p = 0.0185
Pembrolizumab + chemotherapy
23 mo
Placebo + chemotherapy
16.1 mo
Source
Progression-free survival, PD-L1 CPS ≥10primary
HR 0.66 (0.5–0.88)
Pembrolizumab + chemotherapy
9.7 mo
Placebo + chemotherapy
5.6 mo
Source
Overall survival, CPS ≥1
HR 0.86 (0.72–1.04)
Pembrolizumab + chemotherapy
17.6 mo
Placebo + chemotherapy
16 mo

Not significant

Source
EndpointArmnValueHR (95% CI)pSource
Overall survival, PD-L1 CPS ≥10primaryPembrolizumab + chemotherapy22023 months0.73 (0.55–0.95)0.0185link
Placebo + chemotherapy10316.1 months
Progression-free survival, PD-L1 CPS ≥10primaryPembrolizumab + chemotherapy—9.7 months0.66 (0.5–0.88)—link
Placebo + chemotherapy—5.6 months
Overall survival, CPS ≥1Pembrolizumab + chemotherapy—17.6 months0.86 (0.72–1.04)—link
Placebo + chemotherapy—16 months
Replication
Consistent direction with IMpassion130 (atezolizumab, PD-L1+); IMpassion131 was negative, so the PD-L1 CPS ≥10 population and the chemotherapy partner matter. Now being superseded by ADC + pembrolizumab (ASCENT-04).

Connected

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Pages like this

not linked directly; found by shared links

cancers

1
Triple-negative breast cancer (TNBC)

drugs

1
ApprovedMonoclonal antibody (anti-PD-1)
Pembrolizumab · Keytruda / Keytruda Qlex (SC)

terms

1
Combined positive score (CPS)

trials

1
IMpassion131

roadmaps

1
TNBC roadmap: from 'nothing to target' to ADC + immunotherapy first line