Research Highlights From ESMO Breast 2026

The European Society for Clinical Oncology (ESMO) Breast Cancer Annual Congress 2026 took place May 6–8 in Berlin. The meeting brought together leading experts, researchers, and advocates to discuss the latest breakthroughs in breast cancer across the entire care spectrum: from early detection to treatment innovations and long-term survivorship. 

Currently, many studies are looking at what doctors call de-escalating treatment. This means giving people fewer treatments or treatments that cause fewer and less severe side effects. To do this, researchers have been looking for new ways to predict who can safely skip certain treatments.

The researchers behind the PHERGain-2 trial wanted to know if people diagnosed with very treatable types of early-stage, HER2-positive breast cancer who have a pathological complete response (pCR) to treatments given before surgery can skip chemotherapy after surgery. A pCR means that no active cancer cells are present in tissue removed during surgery. It shows doctors that pre-surgery treatments were effective.

All the cancers in the study were very small, node-negative, and strongly HER2-positive, which means they would likely respond well to anti-HER2 medicines given before surgery. So these types of cancers would be more likely to have a pCR and less likely to need chemotherapy after surgery.

Early results from the study show that people with pCR who skipped chemo after surgery had better quality of life than people who received chemotherapy. But because these are early results, we don’t yet know if the rates of the cancer coming back (recurrence) are different between the treatment groups.

Results from the SATEEN trial showed that the combination of Trodelvy (chemical name: sacituzumab govitecan-hziy) and Herceptin (chemical name: trastuzumab) to treat metastatic HER2-positive breast cancer that grew during Enhertu (chemical name: fam-trastuzumab-deruxtecan-nxki) treatment wasn’t effective. Only one of the 27 cancers in the study responded to the combo treatment. Researchers had hoped the combination could be another option for people if Enhertu stops working.

It was one of the first prospective studies looking at using antibody-drug conjugates (ADCs) — Trodelvy and Enhertu — one after the other.  The two drugs target different proteins, but they both use the same type of chemotherapy, a topoisomerase 1 inhibitor. Experts think resistance to the chemotherapy part of the ADC may explain the SATEEN findings. The results also echo real-world studies that have shown limited benefits for people receiving one topoisomerase 1 inhibitor ADC after another.