Research table: Pembrolizumab (Keytruda) for metastatic breast cancer treatment

This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.

Introduction: Pembrolizumab is a checkpoint inhibitor immunotherapy drug used to treat some metastatic breast cancers.

Pembrolizumab in combination with chemotherapy is used to treat metastatic triple negative breast cancers that are PD-L1-positive (programmed cell death ligand 1-positive). All metastatic triple negative breast cancers are tested to learn if they are PD-L1-positive.

Pembrolizumab in combination with chemotherapy

Compared to chemotherapy alone, pembrolizumab in combination with chemotherapy may give people with metastatic PD-L1-positive triple negative breast cancers more time before the cancer worsens and may improve survival.

Pembrolizumab in combination with sacituzumab govitecan

Compared to pembrolizumab plus chemotherapy, pembrolizumab plus sacituzumab govitecan may give people with PD-L1-positive metastatic triple negative breast cancer more time before the cancer worsens.

Learn more about pembrolizumab (including side effects) and metastatic breast cancer treatment.

Learn about guidelines for the treatment of metastatic breast cancer.

Learn about pembrolizumab and early breast cancer treatment.

Study selection criteria: Randomized clinical trials with 100 or more participants with metastatic triple negative breast cancer.

Table note: Objective response rates (percent of people who responded to treatment) and overall survival data are for women with triple negative breast cancers that were PD-L1-positive, defined as a combined positive score (CPS) of 10 or more.

Study	Study Population (number of participants)	Drug(s) Used	Objective Response Rate—Percent who Responded to Treatment (95% CI)	Overall Survival (95% CI)
Randomized clinical trials
KEYNOTE-119 [1]	1,098	Pembrolizumab alone	18%	Overall survival at 31 months: 23%
		Chemotherapy alone (capecitabine, eribulin, gemcitabine, or vinorelbine)	9%	Overall survival at 31 months: 11%
KEYNOTE-355 [2]	847	Pembrolizumab and chemotherapy (nanoparticle albumin-bound paclitaxel, paclitaxel, or gemcitabine–carboplatin)	53%	Overall survival at 18 months: 58%*
		Chemotherapy alone (nanoparticle albumin-bound paclitaxel, paclitaxel, or gemcitabine–carboplatin)	41%	Overall survival at 18 months: 45%*
ASCENT trial – 04/KEYNOTE-D19 trial [3]	443	Pembrolizumab plus sacituzumab govitecan	60%
		Pembrolizumab plus chemotherapy (paclitaxel, nab-paclitaxel, or gemcitabine plus carboplatin)	53%

* Statistically significant difference between the 2 treatment groups

References

Winer EP, Lipatov O, Im SA, et al. for the KEYNOTE-119 investigators. Pembrolizumab versus investigator-choice chemotherapy for metastatic triple-negative breast cancer (KEYNOTE-119): a randomised, open-label, phase 3 trial. Lancet Oncol. 22(4):499-511, 2021.
Cortes J, Rugo HS, Cescon DW, et al. for the KEYNOTE-355 Investigators. Pembrolizumab plus chemotherapy in advanced triple-negative breast cancer. N Engl J Med. 387(3):217-226, 2022.
Tolaney SM, de Azambuja E, Kalinsky K, et al. for the ASCENT-04/KEYNOTE-D19 Clinical Trial Investigators. Sacituzumab govitecan plus pembrolizumab for advanced triple-negative breast cancer. N Engl J Med. 394(4):354-366, 2026.

Updated 07/16/26