Update: Targeted therapy for early-stage HER2-positive breast cancer continues to show benefit

Relevance: Medium-High

Strength of Science: High

Research Timeline: Post Approval

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What is this update about?

The KATHERINE trial compared trastuzumab emtansine (T-DM1, brand name Kadcyla) to trastuzumab (Herceptin) for people with early-stage HER2-positive breast cancer who still showed signs of cancer after surgery and postsurgery treatment. You can read our XRAY review on the initial results of this trial here.

This update from the KATHERINE trial covers a longer period. It compares the length of time without cancer returning and overall survival. People who took T-DM1 had better outcomes.

Why is this update important?

This trial was important because early-stage HER2-positive cancer is often treatable but can return years later. Research to understand why and when this happens and find treatments that more effectively prevent cancer from coming back are important.

Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate (ADC); a newer type of targeted therapy that better targets and kills cancer cells.

Study findings

This update is a second report of the phase 3 KATHERINE clinical trial results.

The KATHERINE trial tested a new drug called T-DM1 (trastuzumab emtansine or Kadcyla) for early-stage HER2-positive breast cancer. The trial was designed for people who still had signs of cancer in their breasts or lymph nodes after surgery and prior drug therapy. It compared a standard targeted therapy to a new treatment.

The 2018 results that were shared in our first report changed the standard treatment for this patient group to T-DM1 instead of trastuzumab. People in the trial had been followed for an average of nearly 3.4 years at the time of the first report.

The new results confirm that T-DM1 works better than trastuzumab alone.

On average, the new results added over 8 years of follow-up.

People who took T-DM1 after surgery went longer without cancer growth or spread than people who took trastuzumab. They also live longer according to results presented at the 2023 San Antonio Breast Cancer Symposium.

The 1,486 people who participated in the phase 3 KATHERINE trial all had signs of cancer in their breast or nodes after surgery. All were treated with chemotherapy and trastuzumab prior to surgery. This trial included people with both hormone-receptor-positive and hormone-receptor-negative disease.

The new results show that:

• People who took T-DM1 were less likely to have cancer return.
  • 54% fewer people had cancer return compared to those who took trastuzumab alone.
  • People from all subgroups (positive or negative nodes, race, age, HER2 score, etc.) benefited. 
• T-DM1 reduced the risk of death by 34% over trastuzumab.

The final survival results will be reported in two years.

What does this mean for me?

If you or someone you care about is already taking trastuzumab emtansine for early-stage HER2-positive breast cancer, these results are reassuring. If you are newly diagnosed with early-stage HER2-positive breast cancer, talk with your doctor about T-DM1, and its benefits over trastuzumab alone.

References

Loibl S, Mano M, Untch M, et al: Phase III study of adjuvant ado-trastuzumab emtansine vs trastuzumab for residual invasive HER2-positive early breast cancer after neoadjuvant chemotherapy and HER2-targeted therapy. 2023 San Antonio Breast Cancer Symposium. Abstract GS03-12. Presented December 8, 2023.

FDA approves ado-trastuzumab emtansine for early breast cancer. U.S. Food and Drug Administration press release. May 6, 2019

Disclosure: FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.

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posted 6/20/24