ASCO Updates Guidance for HR-Positive, HER2-Negative Breast Cancer

ASCO has published version 2026.1.0 of its living guideline on medical therapy for patients with stage I-III hormone receptor-positive, HER2-negative breast cancer. The guideline is organized around the sequence of treatment decisions from diagnosis through completion of systemic therapy.

An expert panel that included patient representation conducted a systematic evidence review. Eligible studies evaluated neoadjuvant or adjuvant chemotherapy, endocrine therapy, immunotherapy, or targeted therapy. Outcomes included pathologic complete response, disease-free survival, distant recurrence-free survival, overall survival, health-related quality of life, and treatment-related adverse effects.

The broad literature search identified 45 randomized clinical trials represented in 68 references and published from 2018 through 2026. Supplemental searches identified 6 individual patient data meta-analyses and 21 retrospective studies. Together, this evidence informed recommendations on which patients should receive treatment, treatment selection, timing and duration, and approaches to support adherence.

The panel described endocrine therapy as the foundation of treatment for stage I-III hormone receptor-positive, HER2-negative disease. For selected patients, chemotherapy and targeted therapies can further reduce recurrence and breast cancer mortality risk. The guideline advises integrating clinicopathologic characteristics, genomic assays, patient preferences, treatment tolerability, and estimated recurrence risk when selecting and sequencing therapy.

A final guideline section addresses estimation of prognosis and treatment benefit across phases of treatment. The document is a living guideline, allowing recommendations to be updated as relevant evidence emerges.

Source: Caswell-Jin JL, Somerfield MR, Khan MA, et al. Medical therapy for hormone receptor-positive, HER2-negative stage I-III breast cancer: ASCO living guideline, version 2026.1.0. J Clin Oncol. Published online August 26, 2026. doi:10.1200/JCO-26-02034