Appraising Adjuvant Endocrine Therapy in Hormone Receptor Positive HER2-Negative Breast Cancer-A Literature Review

Abstract

Background: Approximately 75% of breast cancer (BC) is associated with luminal differentiation expressing endocrine receptors (ER). For ER+ HER2- tumors, adjuvant endocrine therapy (ET) is the cornerstone treatment. Although relapse events steadily continue, the ET benefits translate to dramatically lengthen life expectancy with bearable side-effects. This review of ER+ HER2- female BC outlines suitable adjuvant treatment strategies to help guide clinical decision making around appropriate therapy.

Methods: A literature search was conducted in Embase, Medline, and the Cochrane Libraries, using ER+ HER-, ET BC keywords.

Results: In low-risk patients: five years of ET is the standard option. While Tamoxifen remains the preferred selection for premenopausal women, AI is the choice for postmenopausal patients. In the high-risk category: ET plus/minus OFS with two years of Abemaciclib is recommended. Although extended ET for a total of ten years is an alternative, the optimal AI duration is undetermined; nevertheless an additional two to three years beyond the initial five years may be sufficient. In this postmenopausal group, bisphosphonate is endorsed.

Conclusions: Classifying the risk category assists in deciding the treatment route and its optimal duration. Tailoring the breadth of ET hinges on a wide array of factors to be appraised for each individualized case, including weighing its benefits and harms.

Keywords: HER2-negative; adjuvant cyclin-dependent kinases 4/6 inhibitors; aromatase inhibitors; bisphosphonates; early breast cancer; endocrine therapy; hormone receptor positive; postmenopausal; premenopausal; selective estrogen receptor.

Figure 1

Adjuvant endocrine therapy for premenopausal women with ER+ HER2− breast cancer.

Figure 2

Adjuvant endocrine therapy for postmenopausal women with ER+ HER2− breast cancer.