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Study on Atezolizumab and Trastuzumab Emtansine for Patients with HER2-Positive Breast Cancer at High Risk of Recurrence After Preoperative Therapy

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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 HER2-positive breast cancer, a type of breast cancer that tests positive for a protein called human epidermal growth factor receptor 2, which promotes the growth of cancer cells. The study is evaluating the effectiveness and safety of two treatments: atezolizumab and trastuzumab emtansine. Atezolizumab, also known by its code name RO5541267, is a medication that helps the immune system fight cancer. Trastuzumab emtansine is a combination of two drugs that work together to target and kill cancer cells. The study also includes a comparison with a placebo, which is a substance with no active medication.

The purpose of the study is to determine how well atezolizumab works when given with trastuzumab emtansine, compared to trastuzumab emtansine alone. Participants in the study will receive one of these treatments after they have completed their initial therapy for breast cancer. The study will monitor participants over a period of time to assess their health and any changes in their condition. This will help researchers understand the potential benefits and risks of the treatments.

Participants will be randomly assigned to receive either the combination of atezolizumab and trastuzumab emtansine, trastuzumab emtansine with a placebo, or other variations as part of the study. The treatments will be administered through an infusion, which is a method of delivering medication directly into the bloodstream. The study aims to provide valuable information on the effectiveness of these treatments in preventing the recurrence of breast cancer in patients who are at high risk.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria, including a diagnosis of HER2-positive breast cancer and completion of preoperative therapy.

    The interval between primary surgery and randomization must not exceed 12 weeks.

  2. Step 2

    Randomization

    Participants are randomly assigned to receive either the study medication or a placebo.

    This process ensures that the study results are unbiased and reliable.

  3. Step 3

    Treatment phase

    Participants receive trastuzumab emtansine and either atezolizumab or a placebo.

    Trastuzumab emtansine is administered as an IV infusion.

    Atezolizumab or placebo is also administered as an IV infusion.

    The specific dosage and frequency of administration are determined by the study protocol.

  4. Step 4

    Monitoring and assessments

    Regular monitoring is conducted to assess the effectiveness and safety of the treatment.

    Participants undergo various assessments, including blood tests and imaging studies, to evaluate their response to the treatment.

  5. Step 5

    Follow-up

    After completing the treatment phase, participants enter a follow-up period.

    During this time, ongoing assessments are conducted to monitor for any recurrence of cancer and to evaluate overall health.

  6. Step 6

    Study completion

    The study is estimated to conclude by June 29, 2035.

    Final results will be analyzed to determine the efficacy and safety of the treatment.

Who can join the trial?

7 criteria

  • The patient must have a confirmed diagnosis of invasive breast cancer. This means that cancer cells have spread beyond the original site in the breast.
  • There must be evidence of remaining cancer in the breast or nearby lymph nodes after surgery, following initial treatment. If the cancer was initially found in certain stages (cT1-3/N0-1/M0), there must be cancer left in the lymph nodes.
  • The breast cancer must be **HER2-positive**, which is a specific type of breast cancer that has more of a protein called HER2. The status of hormone receptors and a protein called programmed death ligand 1 must also be checked through a special test on a tumor sample.
  • The patient must have completed chemotherapy and treatment targeting HER2 before surgery.
  • All visible cancer in the breast and lymph nodes must have been surgically removed.
  • There should be no more than 12 weeks between the main surgery and the start of the trial.
  • The trial is open to both female and male patients.

Who cannot join the trial?

7 criteria

  • Patients with other types of cancer besides HER2 positive breast cancer cannot participate. HER2 positive breast cancer is a type of breast cancer that has a higher amount of a protein called HER2, which can make cancer grow faster.
  • Patients who have had previous treatment with the study drugs, atezolizumab or trastuzumab emtansine, are not eligible. Atezolizumab is a medicine that helps the immune system fight cancer, and trastuzumab emtansine is a drug that targets cancer cells with the HER2 protein.
  • Patients with severe or uncontrolled medical conditions that could interfere with the study are excluded. This means if someone has a serious health problem that is not well-managed, they cannot join the study.
  • Pregnant or breastfeeding women cannot participate in the study to ensure the safety of the baby.
  • Patients who are participating in another clinical trial at the same time are not allowed to join this study.
  • Patients with known allergies to the study drugs or their ingredients are excluded to prevent allergic reactions.
  • Patients with a history of certain heart problems may not be eligible, as these conditions could be worsened by the study drugs.
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Investigated drugs

  • Atezolizumab

    is a medication used in this trial to help the immune system attack cancer cells. It is being tested to see if it can improve the treatment of HER2-positive breast cancer, which is a type of breast cancer that has a higher risk of coming back after initial treatment.

  • Trastuzumab Emtansine

    is a medication that combines two different types of cancer treatments. It targets HER2-positive breast cancer cells and delivers a chemotherapy drug directly to them. This helps to kill the cancer cells while minimizing damage to healthy cells. The trial is testing its effectiveness when used with atezolizumab.

What is already known about the treatment

  • Atezolizumab

    Atezolizumab is administered intravenously and is currently being studied in clinical trials for its effectiveness in treating early HER2-positive breast cancer. It is an immunotherapy drug that works by blocking the interaction between PD-L1 and its receptors, thereby enhancing the immune system's ability to attack cancer cells. Atezolizumab is classified as a monoclonal antibody and is being evaluated for its potential to reduce the risk of cancer recurrence when used alongside trastuzumab emtansine.

  • Trastuzumab Emtansine

    Trastuzumab emtansine is given through an intravenous infusion and is an established treatment for HER2-positive breast cancer, particularly in cases with a high risk of recurrence. It combines the HER2-targeting properties of trastuzumab with the cytotoxic agent emtansine, delivering targeted chemotherapy directly to cancer cells. This medication is classified as an antibody-drug conjugate and is being tested in combination with atezolizumab to assess its efficacy in preventing cancer recurrence.

Investigated diseases

Early Human Epidermal Growth Factor Receptor 2 (HER2) Positive Breast Cancer – This is a type of breast cancer characterized by the overexpression of the HER2 protein, which promotes the growth of cancer cells. It is considered an early stage when the cancer is confined to the breast or nearby lymph nodes and has not spread to distant parts of the body. The disease progresses as the cancer cells grow and potentially spread to other areas, which can lead to more advanced stages if not managed. HER2-positive breast cancer tends to grow and spread more aggressively than other types of breast cancer. The progression of the disease can vary, with some cases remaining localized while others may advance more rapidly. Understanding the specific characteristics of HER2-positive breast cancer is crucial for determining appropriate management strategies.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-503568-18-00Protocol codeWO42633Estimated enrolment1 150 patientsSponsorF. Hoffmann-La Roche AG

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