ESMO Updates Metastatic Breast Cancer Guideline: Molecular Subtyping and ADCs Reshape the 2026 Treatment Landscape
核心洞察
The 2026 ESMO (搜索) Clinical Practice Guideline for metastatic breast cancer (搜索) mandates biopsy and receptor reassessment at first metastatic diagnosis to confirm tumor biology and guide subtype-specific therapy.
CDK4/6 inhibitors remain the backbone of first-line ER-positive/HER2 (搜索)-negative disease, while ESR1 (搜索), PIK3CA, AKT1 (搜索), and PTEN (搜索) testing now directs targeted therapy after endocrine resistance.
Antibody-drug conjugates including trastuzumab deruxtecan, sacituzumab govitecan, and datopotamab deruxtecan are integrated across HER2 (搜索)-positive, HER2-low, ER-positive, and triple-negative settings.
The European Society for Medical Oncology has released an updated ESMO (搜索) Clinical Practice Guideline for metastatic breast cancer (搜索), published in Annals of Oncology, superseding the 2021 version and reflecting a treatment landscape increasingly defined by molecular biomarkers, antibody-drug conjugates (ADCs), and patient-centered care. Led by E. de Azambuja, C.H. Barrios, R. Bartsch, G. Curigliano, R. Dent, A. Gennari, S. Loi, S. Paluch-Shimon, B. Pistilli, C. Saura, P. Schmid, T. Spanic, M. Toi, S.M. Tolaney, and N. Harbeck on behalf of the ESMO Guidelines Committee, the guideline provides updated recommendations across diagnosis, molecular testing, systemic therapy, site-specific management, monitoring, and survivorship.
The guideline underscores that metastatic breast cancer (搜索) is no longer managed as a single disease. Treatment decisions now depend on receptor status, genomic alterations, prior therapy exposure, disease tempo, metastatic sites, patient preferences, and access to specific agents. ESMO (搜索) states that all recommendations need to be discussed with patients in a shared decision-making approach, balancing survival benefit, toxicity, quality of life, and personal goals.
Biopsy and Receptor Reassessment at Metastatic Diagnosis
A foundational recommendation is that at first diagnosis of metastatic breast cancer (搜索), biopsy should be performed when feasible to confirm histology and reassess tumor biology, including estrogen receptor (ER), progesterone receptor (PR), and HER2 (搜索) status. If receptor status differs between the primary tumor and the recurrence, patients can generally be managed according to the receptor status of the recurrent disease biopsy.
This is clinically significant because receptor conversion can alter treatment strategy. A tumor initially classified as HER2 (搜索)-negative may later demonstrate HER2-low or HER2-positive biology. Similarly, hormone receptor status may change, affecting the role of endocrine therapy.
The guideline also recommends PD-L1 (搜索) testing in metastatic triple-negative breast cancer (搜索) (TNBC) and germline BRCA1/2 (搜索) and PALB2 (搜索) testing in HER2 (搜索)-negative metastatic disease when specific treatments are available. Somatic BRCA1/2 testing is also recommended in HER2-negative disease if treatment options depend on the result.
Molecular Testing Becomes Central in ER-Positive/HER2-Negative Disease
For ER-positive, HER2 (搜索)-negative metastatic breast cancer (搜索), the guideline assigns a clear role to molecular testing. Evaluation of PIK3CA mutations is recommended if PI3K inhibitors are available. Evaluation of ESR1 (搜索) mutations using circulating tumor DNA (ctDNA) or tumor tissue is recommended after progression on an aromatase inhibitor with or without a CDK4/6 inhibitor. Testing for PIK3CA pathway alterations, including PIK3CA, PTEN (搜索), and AKT1 (搜索), is recommended mainly in the endocrine-resistant setting when specific treatments are available.
This reflects a shift from broad endocrine sequencing to increasingly biomarker-selected therapy. ESR1 (搜索) mutation testing now informs use of oral SERDs such as elacestrant or imlunestrant, while PIK3CA, AKT1 (搜索), and PTEN (搜索) alterations can guide targeted combinations. The guideline also recommends reassessing HER2 (搜索) status as HER2-low, HER2-ultralow, or HER2-0 in patients who are not candidates for endocrine therapy, because HER2 expression level can influence ADC selection.
First-Line ER-Positive/HER2-Negative: CDK4/6 Inhibitors Remain Core
For patients with de novo ER-positive, HER2 (搜索)-negative metastatic breast cancer (搜索) or recurrence more than 12 months after adjuvant endocrine therapy, ESMO (搜索) recommends an aromatase inhibitor (AI) plus a CDK4/6 inhibitor. The guideline lists AI–ribociclib first by preference, followed by AI–abemaciclib and AI–palbociclib.
For patients who recur while on adjuvant endocrine therapy or within 12 months of completing it, fulvestrant plus a CDK4/6 inhibitor is recommended in PIK3CA-wild-type disease. In PIK3CA-mutated disease, the guideline recommends fulvestrant–palbociclib–inavolisib, while fulvestrant plus a CDK4/6 inhibitor remains an option. Ovarian function suppression or ablation is emphasized for premenopausal and perimenopausal women receiving endocrine-based therapy.
Second-Line and Beyond: Targeted Therapy Before Chemotherapy
In second-line ER-positive/HER2 (搜索)-negative disease, ESMO (搜索) recommends selecting therapy based on disease aggressiveness, extent of disease, organ function, prior endocrine sensitivity, molecular profile, and toxicity. Fulvestrant–capivasertib is recommended for tumors with PIK3CA, AKT1 (搜索), or PTEN (搜索) alterations after progression during or after aromatase inhibitor therapy. Fulvestrant–alpelisib can be recommended for PIK3CA-mutated tumors in selected patients.
For ESR1 (搜索)-mutated metastatic breast cancer (搜索) after at least one line of endocrine therapy, elacestrant or imlunestrant are recommended, preferably in patients who had a prolonged response to prior CDK4/6 inhibitor therapy. PARP inhibitors are recommended for germline BRCA1/2 (搜索)-mutated disease, with olaparib and talazoparib listed as options. The guideline also supports PARP inhibitor use in germline PALB2 (搜索)-mutated disease and somatic BRCA1/2-mutated tumors in selected settings, although some of these indications are not EMA or FDA approved.
ADCs Reshape Treatment Across Subtypes
The updated guideline reflects the growing role of ADCs in ER-positive, HER2 (搜索)-negative metastatic breast cancer (搜索). For patients who have previously received chemotherapy, sacituzumab govitecan is recommended after at least one prior line of chemotherapy, and datopotamab deruxtecan is also recommended after at least one prior chemotherapy line. Trastuzumab deruxtecan (T-DXd) is recommended for HER2-low metastatic breast cancer after at least one prior line of chemotherapy if not already used.
For patients who have not yet received chemotherapy, T-DXd may be considered for HER2 (搜索)-low or HER2-ultralow disease after at least two lines of endocrine therapy for metastatic disease, or earlier in patients with endocrine-resistant disease patterns.
HER2-Positive Disease: T-DXd and Tucatinib Central Across Lines
For HER2 (搜索)-positive metastatic breast cancer (搜索), ESMO (搜索) continues to recommend docetaxel–pertuzumab–trastuzumab as a first-line option regardless of ER status. The guideline also recommends T-DXd plus pertuzumab as a first-line option, noting regulatory differences between FDA and EMA approval.
After progression on taxane–trastuzumab, T-DXd is the preferred second-line option when available, regardless of the presence of brain metastases, if not used in the first-line setting. Tucatinib–trastuzumab–capecitabine is also recommended in the second line, and T-DM1 remains recommended if T-DXd is not available. For patients with intracranial progression without extracranial progression, local treatment of brain metastases and continuation of the same anti-HER2 (搜索) treatment can be recommended.
Triple-Negative Breast Cancer: PD-L1, BRCA, and ADCs Guide Treatment
For metastatic TNBC, immune checkpoint inhibitor plus chemotherapy is the preferred option for PD-L1 (搜索)-positive disease. ESMO (搜索) recommends pembrolizumab–sacituzumab govitecan for patients with PD-L1 CPS ≥10 and disease-free interval of at least 6 months after adjuvant treatment, while pembrolizumab plus chemotherapy remains recommended for the same PD-L1 CPS ≥10 group. Atezolizumab–nab-paclitaxel is recommended for patients with immune cell PD-L1 positivity of at least 1% and disease-free interval of at least 12 months after adjuvant treatment, with regulatory caveats.
For germline BRCA1/2 (搜索)-mutated, PD-L1 (搜索)-negative metastatic TNBC, olaparib, talazoparib, or carboplatin-based chemotherapy are recommended. For germline BRCA1/2-wild-type and PD-L1-negative disease, datopotamab deruxtecan or sacituzumab govitecan are recommended for most patients if available. In later lines, sacituzumab govitecan is the preferred recommended option if not used previously, and T-DXd can be recommended as a third-line option in HER2 (搜索)-low metastatic TNBC.
Brain Metastases: Integrating Local and Systemic Therapy
The guideline provides detailed recommendations for brain metastases and leptomeningeal disease. ESMO (搜索) recommends brain imaging for symptomatic patients, with MRI as the preferred technique. Routine brain imaging is not recommended for asymptomatic patients at initial metastatic diagnosis or during monitoring, although subtype-oriented brain imaging may be considered if detection of CNS disease would change systemic therapy choice, particularly in HER2 (搜索)-positive disease and TNBC.
For brain metastases, stereotactic radiotherapy is recommended over whole-brain radiotherapy. The guideline also states that simultaneous administration of stereotactic radiotherapy and ADCs cannot be recommended. In HER2 (搜索)-positive breast cancer with brain metastases, T-DXd is recommended as the preferred second-line option, with tucatinib–trastuzumab–capecitabine recommended if T-DXd is not available or not indicated.
Individualized Monitoring and Survivorship
The guideline recommends CT of the chest and abdomen and bone scintigraphy as minimum baseline imaging work-up, with blood tests including liver function tests. FDG-PET/CT can also be recommended. Treatment response evaluation is recommended every 2–4 months depending on symptoms, disease dynamics, metastatic burden, location, and treatment type.
Importantly, ESMO (搜索) states that shortening monitoring intervals cannot be recommended because there is no evidence of an overall survival benefit and there is potential for emotional and financial harm. The guideline places strong emphasis on supportive care and survivorship, recommending a multidisciplinary approach including specialized oncology nurses, electronic patient-reported outcomes, quality-of-life assessments, proactive symptom management, sexual health care, fertility counseling, and contraception counseling.
The 2026 ESMO (搜索) Clinical Practice Guideline for metastatic breast cancer (搜索) reflects a field in which treatment is increasingly defined by biology, biomarkers, disease subtype, prior therapy, metastatic site, and patient priorities. For clinicians, the message is clear: metastatic breast cancer care is no longer a linear treatment pathway but a dynamic, molecularly informed, patient-centered strategy that must adapt as the disease and therapeutic landscape evolve.