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Study of Pembrolizumab with Chemotherapy for High-Risk Early-Stage ER+/HER2- Breast Cancer Patients

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a type of breast cancer known as ER+/HER2- breast cancer, which is a form of cancer that tests positive for estrogen receptors but negative for a protein called HER2. The study is investigating the effects of a medication called pembrolizumab, also known by its code name MK-3475, in combination with other cancer treatments. Pembrolizumab is a type of medication that helps the immune system fight cancer cells. The trial will compare pembrolizumab with a placebo, which is a substance with no active medication, to see how effective it is when used alongside standard cancer treatments.

The purpose of the study is to evaluate how well pembrolizumab works in combination with chemotherapy and hormone therapy for patients with high-risk early-stage ER+/HER2- breast cancer. Participants in the study will receive either pembrolizumab or a placebo, along with chemotherapy drugs such as epirubicin, paclitaxel, doxorubicin, and cyclophosphamide. These chemotherapy drugs are commonly used to treat breast cancer and work by killing cancer cells or stopping them from growing. The study will follow participants through their treatment and recovery to assess the effectiveness of the treatment combinations.

Throughout the study, participants will undergo various treatments and assessments to monitor their response to the medication and any side effects they may experience. The trial aims to determine if pembrolizumab can improve outcomes for patients with this type of breast cancer, such as achieving a complete response to treatment or extending the time without cancer progression. The study will provide valuable information on the potential benefits of adding pembrolizumab to the standard treatment regimen for high-risk early-stage ER+/HER2- breast cancer.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    The initial phase involves the administration of pembrolizumab or a placebo. This is given as an intravenous infusion, which means the medication is delivered directly into the bloodstream through a vein.

    During this phase, pembrolizumab is combined with neoadjuvant chemotherapy. Neoadjuvant chemotherapy is treatment given before surgery to shrink the tumor.

    The chemotherapy drugs used include epirubicin, paclitaxel, and cyclophosphamide. These are also administered through intravenous infusion.

  2. Step 2

    Surgery

    After completing the initial treatment phase, surgery is performed to remove the tumor. The goal is to achieve a pathological complete response, meaning no cancer is found in the tissue samples taken during surgery.

  3. Step 3

    Adjuvant therapy

    Following surgery, adjuvant therapy is administered. This includes additional doses of pembrolizumab or placebo, combined with endocrine therapy.

    Endocrine therapy involves medications that block hormones which can promote cancer growth. This is particularly relevant for estrogen receptor-positive breast cancer.

  4. Step 4

    Follow-up

    Regular follow-up appointments are scheduled to monitor health and check for any signs of cancer recurrence.

    During these visits, assessments may include physical exams, imaging tests, and laboratory tests to evaluate overall health and response to treatment.

Who can join the trial?

8 criteria

  • The patient must have a type of breast cancer called ER+/HER2- breast cancer, which is a specific kind of breast cancer.
  • The patient must have a localized invasive breast ductal adenocarcinoma, which means the cancer is in the breast ducts and has not spread far. The tumor size should be at least 2 cm, or it should be at certain stages (T1c-T2, cN1-cN2, or T3-T4, cN0-cN2). Inflammatory breast cancer is also allowed.
  • The patient must have a specific grade of breast cancer (Grade 3) confirmed by a pathologist, following certain guidelines.
  • The patient must provide a new or recent core needle biopsy, which is a sample of the breast tumor taken with a needle, to check certain cancer characteristics.
  • The patient must have an ECOG performance status of 0 or 1, which is a scale used to assess how well a patient can perform daily activities. A score of 0 means fully active, and 1 means some restrictions but still able to do light work.
  • Male participants must agree to use contraception during the treatment and for a certain period after the last dose, and they should not donate sperm during this time.
  • Female participants must agree to use effective contraception during the treatment and for a certain period after the last dose.
  • The patient must have adequate organ function, meaning their organs are working well enough to handle the treatment.

Who cannot join the trial?

9 criteria

  • Patients with a different type of breast cancer than ER+/HER2- cannot participate. ER+/HER2- refers to a specific type of breast cancer that has certain characteristics related to hormone receptors and proteins.
  • Patients who are not within the specified age range for the study cannot participate. The age range is determined by the study and may vary.
  • Patients who are not able to follow the study procedures or who have conditions that make it unsafe for them to participate cannot join the study.
  • Patients who are pregnant or breastfeeding are usually excluded from participating in clinical trials.
  • Patients who have participated in another clinical trial recently may not be eligible to join this study.
  • Patients with certain medical conditions that could interfere with the study or increase risk may be excluded.
  • Patients who are unable to provide informed consent, which means they cannot understand the study and agree to participate, are not eligible.
  • Patients who have allergies or reactions to the study medications or similar drugs may be excluded.
  • Patients with a history of certain diseases or conditions that could affect the study results may not be allowed to participate.
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Investigated drugs

  • Pembrolizumab

    is a medication used in this trial to help the body's immune system fight cancer cells. It is being tested to see if it can improve outcomes for patients with a specific type of breast cancer when used alongside other cancer treatments. Pembrolizumab works by blocking a protein that stops the immune system from attacking cancer cells, potentially allowing the immune system to better target and destroy these cells.

  • Neoadjuvant Chemotherapy

    refers to cancer-fighting drugs given before surgery to shrink tumors and make them easier to remove. In this trial, neoadjuvant chemotherapy is used in combination with pembrolizumab to see if this approach can improve the effectiveness of the treatment for breast cancer.

  • Adjuvant Endocrine Therapy

    is a treatment given after the primary treatment, such as surgery, to help prevent cancer from returning. It involves medications that block or lower the amount of hormones in the body, as some breast cancers grow in response to hormones. This therapy is used in the trial to see if it can further reduce the risk of cancer recurrence when combined with pembrolizumab and chemotherapy.

What is already known about the treatment

Pembrolizumab – Pembrolizumab is administered intravenously and is currently being studied in clinical trials for its effectiveness in treating high-risk early-stage estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer. It is an established medication in the field of oncology, with numerous studies supporting its use in various cancers. The main therapeutic indication for pembrolizumab in this trial is to improve outcomes in breast cancer patients when combined with neoadjuvant chemotherapy and adjuvant endocrine therapy. At the molecular level, pembrolizumab works by blocking the PD-1 pathway, which helps the immune system recognize and attack cancer cells. It is classified as an immune checkpoint inhibitor, a type of immunotherapy that enhances the body's natural defenses against cancer.

Investigated diseases

ER+/HER2- Breast Cancer – This is a type of breast cancer characterized by the presence of estrogen receptors (ER+) and the absence of human epidermal growth factor receptor 2 (HER2-). It means that the cancer cells grow in response to the hormone estrogen but do not have an excess of the HER2 protein on their surfaces. This type of breast cancer tends to grow more slowly than other types and may have a different pattern of spread. It is often diagnosed through a combination of imaging tests and biopsy. The progression of this cancer can vary, but it typically involves the growth of tumors in the breast tissue, which may eventually spread to nearby lymph nodes or other parts of the body.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-506921-12-00Protocol codeMK-3475-756Estimated enrolment1 278 patientsSponsorMerck Sharp & Dohme LLC

sourced from the EU Clinical Trials Register and site verification

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