19th St. Gallen International Breast Cancer Conference (2025)

Consensus Recommendations – Early Breast Cancer

ER-Positive / HER2-Negative Disease:
- Genomic Testing:
  - Strong support for multigene assays (Oncotype DX, MammaPrint, etc.) in:
  - Node-negative disease
  - 1 to 3 positive nodes:
    - Especially postmenopausal:
      - In premenopausal patients with 1 to 3 nodes → chemotherapy often still favored even with low genomic risk
Chemotherapy:
- Postmenopausal:
  - N1 (1 to 3 nodes), low genomic risk:
    - Chemotherapy can be omitted
- Premenopausal:
  - N1 disease:
    - Chemotherapy generally recommended:
      - Ovarian suppression contribution acknowledged but not universally accepted as replacement
Ovarian Function Suppression (OFS):
- Recommended in:
  - High-risk premenopausal patients
  - Node-positive disease AI + OFS preferred over tamoxifen alone in higher-risk settings
CDK4/6 Inhibitors:
- Abemaciclib recommended in:
  - High-risk node-positive (monarchE-like criteria)
- Ribociclib:
  - Data discussed but not yet fully standard globally
HER2-Positive Early Breast Cancer:
- Neoadjuvant Therapy:
  - Standard for:
    - Tumors ≥ 2 cm
    - Node-positive disease
  - Preferred regimen:
    - Taxane + dual anti-HER2 (trastuzumab + pertuzumab)
- Residual Disease After Neoadjuvant Therapy:
  - T-DM1 (KATHERINE data) remains standard
- Duration of Trastuzumab:
  - 12 months remains consensus standard
  - 6 months acceptable only in select lower-risk or toxicity cases
- De-escalation:
  - Small node-negative HER2+ (< 2 cm):
    - TH regimen acceptable (APT-like approach)
    - Ongoing interest in response-adapted therapy
Triple-Negative Breast Cancer (TNBC):
- Neoadjuvant Therapy:
  - Standard:
    - Anthracycline + taxane backbone
    - Addition of pembrolizumab:
      - Supported in stage II to III
- Residual Disease:
  - Continue pembrolizumab:
    - KEYNOTE-522 strategy
  - Capecitabine considered if no prior immunotherapy
- BRCA-Mutated:
  - Adjuvant olaparib recommended:
    - OlympiA criteria
Axillary Management:
- Clinically Node-Negative:
  - Sentinel lymph node biopsy (SLNB) standard
  - 1 to 2 Positive Sentinel Nodes (Upfront Surgery):
    - Omission of ALND supported if:
      - Undergoing breast-conserving therapy Whole-breast RT planned – ACOSOG Z0011 principles upheld
- After Neoadjuvant Therapy:
  - If cN+:
    - ycN0:
      - SLNB acceptable if ≥ 3 nodes retrieved + dual tracer
      - Residual nodal disease → ALND still recommended in most settings
Radiation Therapy:
- Hypofractionation:
  - Standard for most patients
- Ultra-hypofractionation (FAST-Forward-like) widely accepted
- Omission of RT:
  - May be considered in:
    - Age ≥ 70
    - Small ER+ tumors
    - Planned endocrine therapy
Regional Nodal Irradiation:
- Recommended in:
  - Node-positive disease
  - High-risk biology
De-escalation Themes:
- Avoid overtreatment in:
  - Low-risk luminal A disease
  - Elderly / frail patients
  - Tailor treatment based on:
    - Biology > anatomy alone
    - Genomic profiling
    - Patient preference
Liquid Biopsy & MRD:
- ctDNA promising but:
  - Not yet standard for treatment decision:
    - Still investigational for escalation / de-escalation
Germline Mutation Carriers
- BRCA1/2:
  - Consider bilateral mastectomy (case-dependent)
  - Adjuvant olaparib in high-risk early disease
  - PALB2 increasingly treated similarly to BRCA in high-risk scenarios
Artificial Intelligence and Imaging:
- MRI not routine for all early-stage patients
- PET-CT not recommended for stage I routine staging
- AI emerging for:
  - Risk stratification
  - Imaging interpretation
  - Treatment personalization
Key Global Themes of St. Gallen 2025:
- Precision > escalation Biology-driven treatment
- Safe de-escalation when supported by data
- Increased use of CDK4/6 inhibitors and immunotherapy in early disease
- Continued minimization of axillary surgery