# Guidance for Canadian Breast Cancer Practice: National Consensus Recommendations for the Systemic Treatment of Patients with HR+/HER2− Metastatic Breast Cancer 2025

## TL;DR

This paper provides updated treatment guidelines for HR+/HER2− metastatic breast cancer in Canada, focusing on optimal therapies and patient-centered care.

## Contribution

The paper presents national consensus recommendations for systemic treatment of HR+/HER2− metastatic breast cancer in Canada.

## Key findings

- New targeted therapies combined with endocrine therapy improve outcomes for HR+/HER2− metastatic breast cancer.
- Optimal treatment sequencing and integration of precision oncology are emphasized in the recommendations.
- Patient quality of life and preferences are highlighted as critical factors in treatment decisions.

## Abstract

Hormone receptor positive (HR+) breast cancer is the most common type of breast cancer. In this subtype of breast cancer, growth is promoted by hormones, like estrogen and progesterone. Although HR+ cancers may also be human epidermal growth factor receptor 2 (HER2)-positive, this manuscript is restricted to HR+ HER2-negative (HER2–) cancers. The main initial treatment for HR+/HER2− breast cancer is endocrine therapy. In the last few years, studies have shown that new targeted therapies, which may be combined with endocrine therapy, provide a greater effect in reducing cancer burden and slowing disease progression. Chemotherapy and antibody–drug conjugates are also used to treat patients with HR+/HER2− breast cancer, typically after the cancer becomes resistant to endocrine-based therapy. In this publication, REAL Canadian Breast Cancer Alliance provides guidance to help healthcare providers, in collaboration with their patients, determine which patients may benefit from these treatments and the optimal order in which to offer them.

Hormone receptor positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) breast cancer accounts for approximately two-thirds of all breast cancers. The treatment landscape for HR+/HER2− metastatic breast cancer has evolved in recent years, with multiple new therapies demonstrating clinical efficacy and improved patient outcomes. To provide evidence-informed guidance on best practices in the management of patients with HR+/HER2− metastatic breast cancer in Canada, consensus recommendations were developed by Research Excellence, Active Leadership Canadian Breast Cancer Alliance (REAL Alliance), a standing nucleus committee with both clinical–academic oncologists from across Canada and representatives from Breast Cancer Canada, a patient advocacy organization. Recommendations were generated using a modified Delphi approach involving up to three anonymous voting rounds, with a predefined consensus threshold of 75%. These consensus recommendations offer guidance on optimal therapeutic strategies for HR+/HER2− metastatic breast cancer within the Canadian landscape, including integration of precision oncology and targeted therapies, optimal sequencing of therapies, and the importance of balancing the benefits of treatments with patient quality of life and preferences.