What the trial was testing
The KEYNOTE-355 enrolled 847 patients with breast cancer. The study was sponsored by Merck and tracked outcomes across the full group of patients who matched the trial's eligibility profile.
It was a large trial designed to confirm whether the treatment works well enough for wider use. Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.
What the results showed
27% reduction in risk of death when Keytruda was added to chemotherapy for TNBC.
New England Journal of Medicine · 2022 · NCT03036488
These findings — that in risk of death for triple-negative breast cancer patients treated with Keytruda plus chemotherapy — were published in the New England Journal of Medicine and represent the headline result of the study.
Researchers tracked outcomes across 847 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.
What this means for patients
For patients with breast cancer, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.
What you can do now
Keytruda plus chemotherapy is now FDA-approved for PD-L1-positive triple-negative breast cancer. If you have TNBC, ask your oncologist about PD-L1 testing — eligibility for this regimen depends on your PD-L1 score.
Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.
Open breast cancer trials
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The primary objective of this trial is to evaluate ovarian suppression following treatment with ZOLADEX 10.8 mg by luteinizing hormone (LH).
Prototype DAA/TAA Vaccine Targeting MUC1 for Immune Interception and Prevention in Ductal Carcinoma In Situ
Women with biopsy-proven ductal carcinoma in situ (DCIS) will be enrolled into two cohorts. One cohort will receive neoadjuvant therapy with an aromatase inhibitor or selective estrogen receptor modulator (SERM) for about 12 weeks prior to surgery at 12 weeks. The second cohort will receive neoadjuvant therapy with an aromatase inhibitor or selective estrogen receptor modulator and MUC1 vaccination (MUC1 peptide + Hiltonol®) pre-operatively at baseline, and weeks 2 and 10, followed by surgery at about 12 weeks. Patients in the vaccine cohort will be offered an optional boost vaccine 6 months after surgery.