Breast Cancer Experts Preview Abstracts to Watch at the 2026 ESMO Breast Cancer Congress

As we gear up for the 2026 European Society for Medical Oncology (ESMO) Breast Cancer Congress, taking place May 6 to 8, 2026, in Berlin, Germany, OncLive® asked leading breast oncologists to share the presentations and conversations at the top of their lists. We gathered exclusive insights from:

• Sarah Sammons, MD, associate director of the Metastatic Breast Cancer Program and a senior physician at Dana-Farber Cancer Institute, as well as an assistant professor of medicine at Harvard Medical School, both in Boston, Massachusetts
• Paolo Tarantino, MD, PhD, a clinical fellow at Dana-Farber Cancer Institute
• Sara M. Tolaney, MD, MPH, chief of the Division of Breast Oncology and associate director of the Susan F. Smith Center for Women’s Cancers and a senior physician at Dana-Farber Cancer Institute, as well as an associate professor of medicine at Harvard Medical School

“I always love going to Berlin for ESMO Breast, because there are always so many interesting subanalyses and updates that sometimes affect practice or at least tell us how to treat patients better and what to prioritize,” Tarantino emphasized. “ESMO Breast 2026 has several interesting oral presentations, mini-oral presentations, and posters. Among these are some I'm very curious about. I cannot wait to go to Berlin and jump into the presentations and posters. If you will be in Berlin, feel free to reach out! One of the things I love most about ESMO Breast is that it always provides a small space where people can meet, discuss, and build collaborations.”

Read on for a glance at studies you should keep an eye on, as well as how their results might propel the future of breast oncology.

What data updates in HER2-positive early-stage breast cancer are important to note?

LBA1 - Residual Cancer Burden (RCB) Following Neoadjuvant Treatment (NAT) With Trastuzumab Deruxtecan (T-DXd) Followed by Paclitaxel + Trastuzumab + Pertuzumab (THP) vs Dose-Dense Doxorubicin + Cyclophosphamide Followed by THP (ddAC-THP) in High-Risk HER2+ Early-Stage Breast Cancer (eBC)

Presentation time: May 6, 2026, 4-4:10 PM Central CEST (Central European Summer Time)

214O - Chemotherapy-Free, Pathological Complete Response (pCR)-Guided Strategy With Trastuzumab-Pertuzumab (HP) and T-DM1 in HER2+ Early Breast Cancer (EBC): PHERGain-2

Presentation time: May 6, 2026, 4:10-4:20 PM CEST

216RO - 5-Year Invasive Disease-Free Survival (iDFS) of the Strategy-Based, Randomized Phase II PHERGain Trial Evaluating Chemotherapy (CT) De-Escalation in HER2[+] Early Breast Cancer (EBC) Patients (pts)

Presentation time: May 7, 2026, 8:30-8:35 AM CEST

Sammons: The [phase 3] DESTINY-Breast11 trial [NCT05113251] was a landmark study investigating the novel treatment regimen of fam-trastuzumab deruxtecan-nxki [T-DXd; Enhertu] followed by paclitaxel plus trastuzumab [Herceptin] and pertuzumab [Perjeta; THP] in HER2-positive early-stage breast cancer. We've already seen data from DESTINY-Breast11 showing that T-DXd followed by THP outperforms dose-dense doxorubicin and cyclophosphamide plus THP (ddAC-THP) in terms of pathologic complete response [pCR] rate.¹ We'll see an update of the study regarding residual breast cancer burden [RCB] at [ESMO Breast 2026], and we await [potential] FDA approval in the coming months for this regimen.²

Tolaney: Some of the data are covering updated analyses from prior presentations. We've seen data from DESTINY-Breast11, and we will see data that will evaluate RCB within that trial that will be interesting. We'll also see updated data from the [phase 2] PHERGain trial [NCT03161353] that investigated pre-operative trastuzumab plus pertuzumab. We'll also see data from the phase 2 PHERGain-2 trial [NCT04733118]. These 3 studies assess different perspectives of escalation of care in the preoperative setting, as well as what I would consider more de-escalation of preoperative treatment for patients with HER2-positive disease.

Tarantino: PHERGain-2 is a trial testing a chemotherapy-free strategy as neoadjuvant treatment for HER2-positive breast cancer with selective trastuzumab/pertuzumab and ado-trastuzumab emtansine [Kadcyla] escalation in patients who require it, as well as the predictive ability of MRI to understand whether this can help tailor treatment in early-stage HER2-positive breast cancer. This trial is going to be extremely interesting. Then there is a subanalysis of a trial that [may change] practice: DESTINY-Breast11, which investigated T-DXd in the neoadjuvant setting, with or without sequential THP. Investigators will present the analysis of outcomes by RCB. This is intriguing and will tell us more about this regimen, which we expect may be approved over the coming months to manage early-stage HER2-positive breast cancer, [and may be] moving to other subtypes of disease, [including] the metastatic setting.

Which clinical trials will provide insights into antibody-drug conjugate sequencing in metastatic breast cancer?

422RO - A Phase 2 Study of Patritumab Deruxtecan (HER3-DXd) in Patients (pts) With Metastatic Breast Cancer (MBC)

Presentation time: May 8, 2026, 9:00-9:05 AM CEST

LBA4 - Efficacy and Safety of Gacituzumab Govitecan (SG) Plus Trastuzumab in Patients With HER2+ Metastatic Breast Cancer After Prior Trastuzumab Deruxtecan (T-DXd): Results From the Phase II SATEEN Trial

Presentation time: May 8, 2026, 9:05-9:10 AM CEST

Sammons: In advanced HER2-positive breast cancer, we will see [data from the phase 2] SATEEN trial [NCT06100874], presented by Dr Tarantino and colleagues from Dana-Farber, evaluating sacituzumab govitecan-hziy [Trodelvy] plus trastuzumab following [prior treatment] with T-DXd. This is one of the first prospective studies looking at the sequencing of topoisomerase inhibitor antibody-drug conjugates [ADCs] one after the other to see whether there's any efficacy [when using] one topoisomerase inhibitor after another. That will be interesting.

Tolaney: We'll see data on ADC sequencing from prospective trials. To date, we've only seen retrospective data from case series, but we will see data from the SATEEN trial investigating the combination of sacituzumab govitecan and trastuzumab in patients who've previously received T-DXd for metastatic HER2-positive breast cancer. We'll also see data [from a phase 2 trial (NCT04699630)] with HER3-DXd in patients who previously received T-DXd for metastatic HER2-positive breast cancer. That will be the first set of prospective studies that I'm aware of that evaluate sequential ADC use. That's been a long-anticipated question that needed to be addressed.

Tarantino: HER3-DXd is an interesting and active ADC, including in patients who have received prior T-DXd. I feel there's going to be a lot more data [with this agent]. ADC sequencing is one of the most controversial and discussed topics in breast oncology because we're starting to have several ADCs. Finally, at ESMO Breast, we will have at least some data [in this area]. We need so much more, and there are large trials ongoing, but ESMO Breast will be one of the first conferences where there are some data in this setting.

What early-phase data in triple-negative breast cancer might lead to paradigm-shifting advances?

426RO - Pumitamig in Combination With DB-1305/BNT325 as First-Line (1L) Treatment for Patients With Advanced or Metastatic Triple-Negative Breast Cancer (a/mTNBC): Efficacy and Safety From a Multicenter, Open-Label, Phase 1/2 Trial

Presentation time: May 8, 2026, 9:40-9:45 AM CEST

Sammons: We will also see exciting novel combination data in the triple-negative setting with a VEGF-targeted bispecific antibody called pumitamig [BNT327/BMS986545] given with a TROP2-directed ADC. The phase 1/2 data [NCT05438329] with pumitamig plus DB-1305/BNT325 appear to show an exciting overall response and disease-control rates for first-line metastatic TNBC [triple-negative breast cancer], where we still have a long way to go to improve outcomes.

What research is evaluating the role of ovarian suppression in breast cancer?

LBA2 - A Window-of-Opportunity (WOO) Trial of Giredestrant +/- LHRH Analogue vs Anastrozole + LHRHa in Premenopausal Patients With ER+/HER2- Early breast Cancer: PREcoopERA

Presentation time: May 6, 2026, 5:02-5:12 PM CEST

Tolaney: I’m also looking forward to seeing data from the phase 2 PREcoopERA study [NCT05896566], which is trying to understand whether we need to use ovarian suppression when giving an oral selective estrogen receptor degrader. This has been a critical question, and it will be important to see [these results].

References

1. Harbeck N, Modi S, Pusztai L, et al. DESTINY-Breast11: neoadjuvant trastuzumab deruxtecan alone (T-DXd) or followed by paclitaxel + trastuzumab + pertuzumab (T-DXd-THP) vs SOC for high-risk HER2+ early breast cancer (eBC). Ann Oncol. 2025;36(suppl 2):S302-S303. doi:10.1016/j.annonc.2025.08.720
2. Enhertu followed by THP supplemental biologics license application accepted in the US for patients with high-risk HER2-positive early-stage breast cancer prior to surgery. News release. Daiichi Sankyo. October 1, 2025. Accessed May 5, 2026. https://www.daiichisankyo.com/files/news/pressrelease/pdf/202510/20251001_E.pdf