SWOG S2206 Trial for Stage II or III Hormone-Receptor-Positive, HER2-Negative Breast Cancer

Overview: The SWOG Trial S2206 is testing whether adding the immunotherapy medicine Imfinzi (durvalumab) to the standard set of three chemotherapy medicines given to people with hormone-receptor-positive, HER2-negative breast cancer increases survival. 

Phase: Phase III; phase III trials compare the safety and effectiveness of a new treatment to the current standard of care. Phase III trials are usually large — some involve thousands of people — and are done at many places in the United States and around the world.

Number of people to enroll: 3,680

ClinicalTrials.gov ID number: NCT06058377

Sponsor of the trial: National Cancer Institute (NCI)

Collaborators: Southwest Oncology Group (SWOG) Cancer Research Network

This trial is enrolling adults who were recently diagnosed with stage II or III hormone-receptor-positive, HER2-negative breast cancer and have not yet been treated for it. To be eligible for the trial, participants have to receive a score of MP2 on the MammaPrint genetic test, which means they are at “ultra-high risk” of cancer recurring.

The MammaPrint test is a genomic test. It predicts how likely a cancer is to grow and spread and how likely it is to recur within 10 years after it was first diagnosed. 

There is some evidence that people who have a MammaPrint ultra-high-risk result may be more likely to respond to chemotherapy and immunotherapy. This means that adding the immunotherapy medicine Imfinzi to chemotherapy may help prevent the cancer from returning for patients with MP2 stage II or III hormone-receptor-positive, HER2-negative breast cancer.

The trial is designed to see if adding Imfinzi to chemotherapy, and administering all the drugs before the surgery to remove breast cancer, reduces the risk of recurrence or metastasis and improves disease-free survival and overall survival.

Imfinzi belongs to a group of drugs called immune checkpoint inhibitors. 

In the study, adults will be randomly assigned to one of two groups:

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  One group will be given a standard combination of three chemotherapy drugs — Taxol, Adriamycin, and Cytoxan (doctors sometimes call this combination ACT).

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  The second group will receive Imfinzi along with the same chemotherapy — Taxol, Adriamycin, and Cytoxan (ACT).

People will get Taxol once a week for three months, and then Adriamycin and Cytoxan once every two weeks for the next two months. People in the second group will get Imfinzi once a month, at the same time as the other chemotherapy drug or drugs, for five months.

All the drugs are given as infusions, normally over half an hour to one hour.

Adults are eligible for this study if they have estrogen-receptor-positive, progesterone-receptor-positive, HER2-negative (or HER2-low) breast cancer that is stage II or III (this information is in your pathology report) and meet one of the following criteria:

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  have had a previous breast biopsy and received a MammaPrint score of MP2 within the past 12 weeks

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  have a breast biopsy sample tested for the study and receive a MammaPrint score of MP2 

People are not eligible for the study if they:

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  have been diagnosed with metastatic breast cancer

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  have been diagnosed with a breast cancer recurrence (cancer that has come back in the same spot after earlier treatment)

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  have already had chemotherapy, immunotherapy, biologic therapy, or hormonal therapy for this cancer

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  have other conditions, such as autoimmune diseases, uncontrolled diabetes, serious heart trouble, or an uncontrolled HIV or hepatitis infection

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  have certain lab test results, such as a leukocyte (a type of white blood cell) count of less than 3,000/mm3, a platelet count of less than 100,000/mm3, an ANC (absolute neutrophil count) of less than 1,500/mm3, or signs of serious liver or kidney problems

Learn about the additional eligibility requirements.

The most common side effects of Imfinzi (durvalumab) are:

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  cough

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  fatigue

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  pneumonia

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  increased risk of upper respiratory infections (such as colds and flu)

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  shortness of breath

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  rash

Taxol, Adriamycin, and Cytoxan also cause side effects. The specific chemotherapy medicine(s) prescribed as part of this study will be chosen by the investigator(s).

The SWOG S2206/NCT06058377 study is being conducted at dozens of sites across the United States.

Call Dr. Erin Cobain (SWOG Cancer Research Network) at 1-800-865-1125 or email her at CancerAnswerLine@med.umich.edu.