HR+, HER2- Metastatic Breast Cancer

Disease State Overview

Breast Cancer Epidemiology

Breast cancer is the most commonly diagnosed carcinoma and leading cause of tumor-related deaths among women worldwide.^1-2 Below are some breast cancer statistics.^1-2

Breast Cancer Accounts For:

24.5% of new global cancer cases among women (2020)

15.5% of global cancer-related deaths in women (2020)

15.2% of all new cancer cases in the United States (2023)

In 2020, about 2.3 million (11.7%) new cases of breast cancer were reported globally among women.¹ Although rare, men can also develop breast cancer.³ Fewer than 1% of breast cancer cases are reported in men in the United States.³

Metastatic Breast Cancer: Introduction

In 2024, there will be ~310,270 new cases of metastatic breast cancer (MBC) in the United States.⁴

There are over 150,000 women in the United States living with metastatic disease^5,6

30% of patients diagnosed with early breast cancer will later develop recurrent and/or metastatic disease⁷

The median survival after MBC diagnosis is ~2 years, with survival rates for recurrent MBC slightly lower compared to that of de novo MBC⁸

De novo MBC accounts for 3%-6% of new breast cancer diagnoses in high-income countries, including the United States⁸

MBC is incurable, and therapeutic goals are mostly palliative^9,10

MBC Classification by Subtypes

Breast cancer is grouped into subtypes based on hormone receptor (HR) status (estrogen receptor [ER] and progesterone receptor [PgR]) and presence or absence of human epidermal growth factor receptor 2 (HER2) overexpression.¹¹

Estrogen and progesterone hormone receptors (HRs). Human epidermal growth factor receptor 2 (HER2).

The 4 subtypes in MBC and their prevalence are shown.¹²

Incidence of MBC by Subtype Among US Patients (SEER 2010 Data)

The 4 subtypes of MBC and their prevalence. — Incidence of MBC by subtype among US patients¹²:

HR+, HER2- (73%)
HR-, HER2- (TNBC, 12%)
HR+, HER2+ (10%)
HR-, HER2+ (5%)

MBC Survival Rates by Subtypes

At 48 months, patients with HR+, HER2+ MBC displayed the best survival rate of 45.5%, followed by HR+, HER2- MBC at 35.9%, then HR-, HER2+ MBC at 33.9%, and finally worst survival for triple-negative breast cancer (TNBC) at 11.2%.¹³

Breast Cancer—Specific Survival Curves for Stage 4 Disease by Molecular Subtypes

Breast cancer-specific survival rate as a percentage of various breast cancer biological subtypes plotted against months since diagnosis. — Breast cancer-specific survival curves for Stage 4 disease by molecular subtypes. X-axis displays months since diagnosis, from 0 months to 48 months, and Y-axis displays breast cancer–specific survival, from 0% to 100%. All molecular subtypes begin at 100% survival rate at 0 months with a gradual decline until 48 months. At 48 months, patients with HR-positive, HER2-positive subtype displayed the best survival rate at 45.5%, followed by HR-positive, HER2-negative at 35.9%, then HR-negative, HER2-positive at 33.9%, and finally worst survival rate was reported for the triple-negative subtype at 11.2%.¹³

In addition, MBC may be categorized via molecular subtypes. Molecular subtypes were initially defined by gene expression patterns, but they can also be approximated using immunohistochemistry assays for ER, PgR, HER2, and Ki-67. However, variability in the definitions of the different subtypes has been noted.^14-16 The 4 molecular subtypes include luminal A, luminal B, HER2 enriched, and triple negative/basal like.^14-16

Molecular Subtypes of Breast Cancer

The 4 molecular subtypes and their HR and HER2 status. — Luminal A breast cancer, which displays ER-positive or PgR-positive and HER2-negative status, constitutes 50-60% of all breast cancers. Luminal B breast cancer, which displays ER-positive or PgR-positive and HER2-positive or HER2-negative status, constitutes 15-20% of all breast cancers. HER2-enriched breast cancer, which displays ER-negative or PgR-negative and HER2-positive status, constitutes 15-20% of invasive breast cancer. Triple negative/basal like breast cancer, which displays ER-negative or PgR-negative, HER2-negative, and basal markers positive status, constitutes approximately 15% of invasive breast cancer.^14-16

Doctor discussing breast cancer subtypes with a patient.

Breast cancer can be classified into 4 subtypes depending on the patient’s HR and HER2 status.¹¹

HR+, HER2- is the most common subtype of MBC, accounting for 73% of all cases.¹² As healthcare providers, it is important to understand the MBC subtypes and how they may be used to guide treatment decisions. Please see the related resources below for additional information on MBC.

References

Sung H, et al. CA Cancer J Clin. 2021;71(3):209-249.
https://seer.cancer.gov/statfacts/html/breast.html. (Accessed March 21, 2024).
https://www.breastcancer.org/types/male-breast-cancer. (Accessed October 27, 2023).
https://www.stopbreastcancer.org/wp-content/uploads/2024/01/2024-Breast-Cancer-Facts-Figs.pdf. (Accessed April 30, 2024).
Mariotto AB, et al. Cancer Epidemiol Biomarkers Prev. 2017;26(6):809-815.
Mayer M, Grober S. Silent Voices: Advanced Breast Cancer Needs Assessment Survey Report. 2006.
Nelson DR, et al. PLoS One. 2022;17(2):e0264637.
Daily K, et al. Clin Breast Cancer. 2021;21(4):302-308.
Cardoso F, et al. Ann Oncol. 2018;29(8):1634-1657.
Irvin W Jr, et al. Oncologist. 2011;16(9):1203-1214.
https://seer.cancer.gov/statfacts/html/breast-subtypes.html. (Accessed October 27, 2023).
Howlader N, et al. J Natl Cancer Inst. 2014;106(5):dju055.
Howlander N, et al. Cancer Epidemiol Biomarkers Prev. 2018;27(6):619-626.
Feng Y, et al. Genes Dis. 2018;5(2):77-106.
Eliyatkin N, et al. J Breast Health. 2015;11(2):59-66.
Yersai O, Barutca S. World J Clin Oncol. 2014;5(3):412-424.

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Disease State Overview

Metastatic Breast Cancer: Introduction

References

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Disease State Overview

Metastatic Breast Cancer: Introduction

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References

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