A New First-Line Combination Held HER2-Positive Metastatic Breast Cancer Back Longer

CATEGORY: WOMEN’S HEALTH

Patients starting treatment for metastatic HER2-positive breast cancer stayed ahead of their disease far longer on a newer drug pairing. A trial that enrolled 1,157 patients found trastuzumab deruxtecan plus pertuzumab held the cancer in check for a median of 40.7 months, against 26.9 months on the standard three-drug regimen.¹ That’s about three and a half years versus just over two. The risk of the cancer progressing, or of death, was 44% lower.

A Drug That Delivers Chemotherapy to One Address

HER2 is a protein that tells cells to grow. Some breast cancers make huge amounts of it, which once marked them as aggressive. Trastuzumab deruxtecan is an antibody that seeks out HER2 and carries a chemotherapy payload with it, so most of the poison arrives at the tumor rather than everywhere at once. Think of a courier delivering to one address instead of leafleting the whole street. The trial paired it with pertuzumab, an established antibody that blocks HER2 a second way.

How the Two Treatments Were Compared

Everyone enrolled had HER2-positive breast cancer that had spread and hadn’t yet been treated in that advanced stage. A random draw, not the treating doctors, decided who got which regimen. The comparison group received the standard of the past decade: chemotherapy plus the antibodies trastuzumab and pertuzumab. Regular scans then tracked how long each treatment kept the cancer from growing. At two years, 70.1% of patients on the new pairing were living without their disease advancing. On the standard regimen, 52.1% were.¹ Tumors also shrank in more patients, 85.1% versus 78.6%, and vanished on imaging in nearly twice as many.

The Cost Side of the Ledger

Severe side effects overall were about as common in both groups, near 63%. One stands apart. Interstitial lung disease, an inflammation that can scar the lungs, affected 12.1% of patients on the new combination and killed two of them. On standard treatment it touched 1%, all mild cases.¹ Whether the new pairing helps people live longer isn’t known yet; the survival data are still maturing, and a third arm of the trial, testing trastuzumab deruxtecan alone, remains under wraps. What’s proven today is longer control, not longer life. US regulators weighed that balance and approved the combination in December 2025 as a first-line option, the first change at that position since pertuzumab’s arrival in 2012. AstraZeneca and Daiichi Sankyo, which make trastuzumab deruxtecan, funded the study.

Key Takeaways

• Longer survival hasn’t been shown yet. The trial has so far proven longer disease control; it will keep following patients to learn whether lives are extended.
• Trastuzumab deruxtecan plus pertuzumab kept newly treated metastatic HER2-positive breast cancer from progressing for a median of 40.7 months, versus 26.9 months on the long-standing standard regimen.
• At the two-year mark, 70.1% of patients on the new pairing had no disease progression, compared with 52.1% on standard care.
• Lung inflammation was the notable risk: 12.1% of patients on the new combination developed it, with two fatal cases, versus 1% with only mild cases on the standard regimen.

References

1. Tolaney SM, Jiang Z, Zhang Q, Barroso-Sousa R, et al. Trastuzumab Deruxtecan plus Pertuzumab for HER2-Positive Metastatic Breast Cancer. N Engl J Med. 2025; online October 29; doi:10.1056/NEJMoa2508668. link