KEYNOTE-355
In previously untreated advanced TNBC with PD-L1 CPS ≥10, does pembrolizumab plus chemotherapy improve survival versus chemotherapy alone?
Trial design and population
Key results
In CPS ≥10 disease, median OS was 23.0 vs 16.1 months (HR 0.73, 95% CI 0.55–0.95; P=.0185). Median PFS was 9.7 vs 5.6 months (HR 0.65, 95% CI 0.49–0.86).
Source-reported outcome visualization
Median overall survival (CPS ≥10) · Median
Bars are scaled to the larger reported group value; endpoint, unit and horizon are labelled. Values are source-reported, not estimated from medians.
Absolute Effect
Median OS difference 6.9 months is not an NNT; no fixed-time OS risk difference is used here.
NNT: Not calculated; median OS difference is not a valid NNT. Use only at the stated endpoint/time horizon; median survival differences are not converted into NNT.
NNH: Not quantifiable. Grade ≥3 treatment-related AEs occurred in roughly two-thirds of patients in both arms. Pembrolizumab adds immune-mediated endocrinopathy, pneumonitis, hepatitis and colitis; chemotherapy adds neuropathy and cytopenias.
Time-to-event hazard ratios and median survival are not treated as absolute risk differences. Where no defensible fixed-time NNT/NNH is available, the source-reported endpoint is visualized instead.
Safety and treatment burden
Grade ≥3 treatment-related AEs occurred in roughly two-thirds of patients in both arms. Pembrolizumab adds immune-mediated endocrinopathy, pneumonitis, hepatitis and colitis; chemotherapy adds neuropathy and cytopenias.
Follow-up, maturity and limitations
Follow-up: Final OS analysis in CPS ≥10 population.
Benefit is tied to PD-L1 CPS ≥10 for first-line metastatic TNBC. Do not extrapolate to CPS <10 or conflate with atezolizumab trials.
Clinical interpretation
Current-practice context · reviewed 20 October 2026
This page separates the original trial findings from contemporary treatment sequencing. Confirm current guidelines, local regulatory status, biomarker requirements, prior treatment exposure and patient-specific contraindications before applying the evidence. Historical comparators may no longer represent the current standard; subgroup findings and immature endpoints are labelled rather than generalized.