ESMO Breast Cancer Congress 2026: Editor highlights

The 2026 edition of the ESMO Breast Cancer Congress convened leading oncologists, researchers and healthcare professionals from around the world to explore key breakthroughs in breast cancer treatment and care. Held over 3 days, the content presented at the congress underscored the field’s rapid evolution toward personalized, effective and less toxic therapeutic approaches.

From novel endocrine strategies in premenopausal women to emerging radioligand therapies and the promise of treatment de-escalation in HER2-positive disease, ESMO Breast Cancer 2026 highlighted both the opportunities and challenges facing modern breast cancer care.

A spotlight on ovarian function suppression and oral SERDs 

PREcoopERA trial: Rethinking endocrine therapy in premenopausal women

On the first day of the conference, Elisabetta Munzone (Instituto Europeo di Oncologia) presented a key late-breaking abstract – summarizing results from the PREcoopERA window-of-opportunity trial.

This study addressed a critical question in the treatment of premenopausal women with ER-positive, HER2-negative early breast cancer: Is ovarian function suppression (OFS) always necessary when using a potent SERD in this patient group?

The clinical context is pressing. Breast cancer incidence is rising among young women, particularly ER-positive cases. While standard treatments combining OFS with tamoxifen or aromatase inhibitors improve outcomes, they are associated with significant endocrine-related toxicity. Adherence to LHRH-based treatments remains a major challenge, particularly in younger patients, creating an urgent need for endocrine therapies that are both effective and tolerable in a premenopausal hormonal environment.

The PREcoopERA trial compared three arms: giredestrant (an oral SERD) plus triptorelin (an LHRH analogue), giredestrant alone, and anastrozole plus triptorelin. Ki67 reduction was used as the marker of anti-proliferative activity.

Key findings included:

• Giredestrant plus triptorelin achieved the greatest anti-proliferative effect, with a Ki67 reduction of 79.6% compared to 73.7% for anastrozole plus triptorelin, though this difference was not statistically significant (p = 0.18)
• Giredestrant alone achieved a 68.2% reduction in Ki67 but did not meet the pre-specified non-inferiority margin compared to giredestrant plus triptorelin
• A correlation between ER degradation and Ki67 reduction (r = 0.40) supported the on-target activity of giredestrant
• Age emerged as an important variable: older premenopausal patients showed deeper Ki67 suppression with giredestrant alone
• Ongoing analyses are exploring the relationship between hormonal levels and proliferative dynamics

Munzone concluded that giredestrant demonstrates biological activity in premenopausal women both with and without OFS. These findings set the stage for further investigation into tailoring endocrine therapy based on individual patient characteristics, including age and hormonal environment.

Further information can be found here: https://clinicaltrials.gov/study/NCT05896566

Special populations: Pregnancy and frailty

Breast cancer during pregnancy: Balancing maternal treatment and fetal safety

Fedro A. Peccatori (European Institute of Oncology, Milan, Italy) delivered an important session on the complex intersection of breast cancer and pregnancy. He emphasized that a cancer diagnosis during pregnancy requires a sensitive, multidisciplinary approach, with clear communication about all available options, including pregnancy termination.

For women who choose to continue their pregnancy, treatment should mirror that offered to non-pregnant women as closely as possible, while carefully considering potential adverse effects on the fetus. He emphasized that medical decisions depend heavily on gestational age, histology, symptoms, staging and the woman’s wishes.

Key biological and treatment insights included:

• Pregnancy-associated breast cancer (PrBC) shows distinct biology, with a higher number of non-silent mutations and a markedly different tumor immune microenvironment compared to non-pregnancy-associated breast cancer
• Chemotherapy is contraindicated in the first trimester due to a high risk of birth defects, but can be administered more safely in the second and third trimesters when the placenta acts as a protective filter
• Taxanes can be given during pregnancy, but tamoxifen cannot be administered due to an increased risk of fetal loss
• Long-term follow-up of children exposed to chemotherapy in utero showed no significant difference in behavior, general health, hearing, growth, neurological development and cardiac function
• Clinical trials in pregnant women with cancer remain extremely challenging to conduct

Peccatori concluded that each pregnancy-associated breast cancer patient requires a highly personalized approach, tailored to multiple individual factors.

Navigating treatment in frail patients

Etienne G. Brain (Institut Curie, France) challenged conventional thinking about age and treatment decisions in his presentation on frailty in breast cancer patients. He emphasized that age is not synonymous with frailty, though the two are related.

Frailty is more prevalent in women and reflects an individual’s intrinsic capacity, which decreases with age. Approximately one in eight women with breast cancer suffers from frailty, which is distinct from both comorbidity and disability.

Why does frailty matter? Brain highlighted that a sizeable proportion of older patients with breast cancer die of non-cancer-related causes. The more aggressive the treatment, the more attention frailty deserves. Studies show that 40% of older women declined after chemotherapy, with only 50% recovering. Treatment duration also matters: regimens exceeding 3 months significantly increase the risk of frailty effects in older populations.

Older patients present distinct biological and clinical features, along with increased toxicity burden. Yet they remain severely underrepresented in clinical trials due to multi-complexity, competing risks and high uncertainties.

Key recommendations included:

• Frailty should be measured at baseline and as an outcome in drug trials
• The G8 frailty screening tool stands out as a pragmatic approach, though no universally accepted perfect tool exists
• Geriatric assessment-guided management has positive effects on treatment completion, toxicity, health-related quality of life, patient satisfaction and communication, without compromising efficacy
• Cognitive impairment is common (50% in patients aged 90+) and should not be underestimated

The UK’s Age Gap decision tool, which incorporates tumor characteristics, age, comorbidities and activities of daily living, represents one approach to more nuanced treatment decision-making in older patients.

Emerging therapeutic modalities

Bispecific antibodies: Disrupting multiple pathways simultaneously

The congress featured an in-depth exploration of bispecific antibodies and antibody-drug conjugates (ADCs) for the treatment of breast cancer. These novel agents offer a strategy to disrupt multiple signaling cascades simultaneously, potentially overcoming drug resistance and tumor heterogeneity.

Key insights:

• Bispecific antibodies targeting HER2 have demonstrated preliminary efficacy, leading to diversification of targets including PD-L1, B7-H4 and VEGF
• T-cell engager bispecific antibodies bring T-cells directly into contact with tumor cells, activating the immune system in areas where it might otherwise be ineffective
• Identifying the optimal antigen pairs for breast cancer to deliver enhanced efficacy over conventional therapies remains an active area of investigation

Radioligand therapy: Learning from prostate cancer

A particularly forward-looking session explored the opportunities and challenges of radioligand therapy (RLT) in breast cancer. In her talk, Sibylle Loibl (Goethe University of Frankfurt, Germany) highlighted that RLT offers mechanistic advantages over ADCs: while ADCs deliver targeted chemotherapy, RLT delivers targeted radiation.

The proof of concept for RLT is well established in prostate cancer, which has become the most clinically validated solid tumor for this approach. Prostate cancer demonstrates that RLT can move from experimental to standard-of-care when a strong target, imaging selection and Phase III evidence align.

Why consider RLT in breast cancer?

• Significant unmet needs exist in metastatic breast cancer, with limited options and poor outcomes despite treatment advances
• Targeted radiation delivery enables the precise targeting of disseminated cancer cells based on surface markers
• RLT can complement existing therapies, particularly in later treatment lines
• RLT represents a precision oncology approach, addressing heterogeneous multisite metastases with systemic therapy

As of April 2026, there are no FDA-approved radioligand therapies specifically for breast cancer, but RLT is emerging as a promising modality, particularly for metastatic, heavily pretreated disease in target-specific subgroups. It offers a theranostic approach (combining diagnosis and therapy), with potential for combination strategies and options for patients with post-ADC resistance.

Key highlights:

• RLT is highly promising but is at an early-stage of investigation for breast cancer
• RLT is particularly attractive for heterogeneous tumors and post-ADC resistance
• Multiple targets are under active investigation
• Major barriers include lack of Phase III data, the need for patient selection and dosimetry standardization as well as organizational challenges of interdisciplinary treatment regimens

Key takeaways

In her closing remarks, Hope Rugo (City of Hope Comprehensive Cancer Center, CA, USA) outlined the major translational themes that emerged from ESMO Breast Cancer 2026:

• How can we improve selection of patients in clinical trials?
• How can we enhance biomarker strategies?
• Response assessment by Ki-67 changes
• Integration of circulating tumor DNA (ctDNA) approaches in clinical workflows
• Integration of artificial intelligence in clinical workflows

Rugo went on to delve deeper into broader themes from the conference, starting with a focus on HER2+ early-stage disease by highlighting the insightful data that has been gained from several clinical trials; DESTINY-Breast 11, PHERGAIN, PHERGAIN-2 and the TRAIN-4 trial.

The congress also emphasized how we can improve risk prediction and survivorship support to move from reactive to proactive survivorship care. Within her roundup, Rugo highlighted presentations from the conference covering:

• ctDNA dynamics in high-risk ER-positive disease to evaluate molecular relapse
• Whether axillary lymph node dissection helps identify patients eligible for adjuvant CDK4/6 inhibitors
• How digital pathology could refine the prediction of risk of recurrence
• The potential of screening for pathogenic germline mutations
• Targeted interventions for young women

Conclusion

ESMO Breast Cancer Congress 2026 showcased a field in rapid transformation, moving toward increasingly personalized treatment options.

The emphasis on special populations – pregnant women, frail older patients and young women — reflected a growing recognition that one-size-fits-all approaches are inadequate. Meanwhile, the integration of advanced technologies such as ctDNA monitoring, digital pathology and artificial intelligence promises to further refine treatment selection and monitoring.

At Oncology Central, we will continue to keep you up to date with how these research findings are being translated into clinical practice. Make sure to visit our breaking news page, journal content and events coverage to stay ahead of the curve.