ASCO: Results of KEYNOTE-355

Abstract No : 1000

Abstract Type : Oral Abstract Session

Indication : Triple Negative Breast Cancer

Intervention : pembrolizumab + chemotherapy

Company : Merck

Technology : Monoclonal Antibody


At data cutoff, 153 pts were randomized to pembro and 154 to chemo. Median (range) study follow-up was 28.4 mo (0.2-48.3) with pembro vs 27.2 mo (0.8-46.6) with chemo. Pembro was superior to chemo for PFS (median 16.5 mo vs 8.2 mo; HR 0.60; 95% CI, 0.45-0.80; P=0.0002). The 12- and 24-mo PFS rates were 55.3% and 48.3% with pembro vs 37.3% and 18.6% with chemo. Confirmed ORR was 43.8% vs 33.1%; median (range) duration of response was not reached (2.3+ to 41.4+) with pembro vs 10.6 mo (2.8 to 37.5+) with chemo. Grade 3-5 treatment related adverse event (AE) rates were 22% vs 66% for pembro vs chemo. One pt in the chemo arm died due to a treatment-related AE.


Pembro combined with several chemo partners showed a statistically significant and clinically meaningful improvement in PFS vs chemo alone in pts with previously untreated locally recurrent inoperable or metastatic TNBC whose tumors expressed PD-L1 (CPS >=10). Pembro + chemo was generally well tolerated, with no new safety concerns.


Enough evidence to support the addition of pembrolizumab to standard chemotherapy for the first line treatment of mTNBC as per KEYNOTE-355 trial.

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