This update brings you the latest in breast cancer guidelines and research from the past two weeks, including announcements from SABCS. We summarize guidelines and highlight key points to help patients, caregivers, and health care professionals stay current with this dynamic, evolving field. Note that both U.S. and international guidelines and research are included, so that we are inclusive of both domestic and international audiences.

Here are our selected top guidelines and research:

1. Sequencing Antibody–Drug Conjugates in Metastatic Breast Cancer: A Systematic Review
Antibody–drug conjugates (ADCs) have redefined the treatment landscape of metastatic breast cancer (mBC), offering durable responses across all subtypes. As multiple ADCs with similar payloads become available for the same patient over the course of the disease, determining the optimal sequencing strategy has become an urgent need, particularly given concerns about cross-resistance and reduced efficacy. According to the article, there appears to be clear efficacy decay with sequential topoisomerase 1 (TOPO-I) ADCs, particularly in human epidermal growth factor receptor 2 (HER2)-low and triple negative breast cancer (TNBC). In HER2-positive disease, trastuzumab deruxtecan (T-DXd) after trastuzumab emtansine (T-DM1) retains clinically meaningful activity.

Key message:
Provides the most comprehensive evidence to date supporting payload-driven sequencing strategies, with direct implications for daily decision-making in metastatic disease.

Reference: Cancer Treatment Reviews, 2025 — Read here

2. Management of Cancer During Pregnancy: ASCO Guideline
Key takeaways:

• Systemic anticancer therapy can be safely administered after 12–14 weeks of gestation, including anthracyclines and taxanes.
• Endocrine therapy, anti-HER2 agents, immunotherapy, and radiotherapy remain contraindicated during pregnancy.
• Strong recommendation for multidisciplinary management involving oncology, maternal–fetal medicine, neonatology, and ethics.
• Emphasizes individualized counseling, fertility preservation, and long-term follow-up of exposed children.

Key message:
This guideline provides an updated, evidence-based framework for managing cancer during pregnancy, directly informing care in young women with breast cancer.

Reference: JCO, 2025 — Read here

3. HER2CLIMB-05: A Phase 3 Study of Tucatinib Versus Placebo in Combination with Trastuzumab and Pertuzumab as First-line Maintenance Therapy for HER2+ Metastatic Breast Cancer
The HER2CLIMB-05 study investigated the efficacy and safety of adding tucatinib to trastuzumab and pertuzumab as first-line (1L) maintenance therapy in patients with human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC). According to the study, the addition of tucatinib to trastuzumab/pertuzumab maintenance significantly improved progression-free survival (PFS). Benefit was observed regardless of hormone receptor status or baseline brain metastases.

Key message:
This study establishes a new maintenance intensification strategy in HER2-positive metastatic disease.

Reference: JCO, 2025 — Read here

4. Imlunestrant with or without Abemaciclib in Advanced Breast Cancer: Updated Efficacy Results from the Phase 3 EMBER-3 Trial
The EMBER-3 trial showed that imlunestrant, especially when combined with abemaciclib, can control advanced estrogen receptor–positive, human epidermal growth factor receptor 2 negative (ER+/HER2-) breast cancer for longer than standard hormone treatments in patients who have already tried other endocrine therapies. It also suggests this regimen could be an effective all oral option that delays the need for chemotherapy while keeping side effects manageable. In ESR1-mutant ER+/HER2- disease, imlunestrant showed a numerically meaningful overall survival (OS) improvement vs standard endocrine therapy. The addition of abemaciclib doubled median progression-free survival (PFS) versus imlunestrant alone.

Key message:
This study reinforces oral SERD-based strategies as a chemotherapy-sparing option after CDK4/6 inhibitor progression, particularly in ESR1-mutant disease.

Reference: Annals of Oncology, 2025 — Read here