OUTCOME OF EARLY STAGE ESTROGEN-RECEPTOR POSITIVE, HER2-NEGATIVE BREAST CANCER WITH AND WITHOUT ADJUVANT ENDOCRINE THERAPY tim.hh.w@gmail.com

 

OUTCOME OF EARLY STAGE ESTROGEN-RECEPTOR POSITIVE, HER2-NEGATIVE BREAST CANCER WITH AND WITHOUT ADJUVANT ENDOCRINE THERAPY

4

New Zealand

Oral or Poster

Adjuvant endocrine therapy (ET) is the current standard of care following hormone receptor positive, HER-2 negative breast cancer. Unfortunately, ET is related to several serious side effects. This study will assess the role of adjuvant ET on estrogen-receptor positive, HER-2 negative early breast cancer.

Data was extracted from the Auckland Breast Cancer Registry between 2000-2024. Patients with T1N0 estrogen-receptor positive, HER-2 negative breast cancers identified and divided into two subgroups: Grade 1 (T1a, T1b and T1c) and Grade 2 (T1a and T1b) with adjuvant ET and without endocrine therapy (non-ET). The primary outcomes were overall survival (OS) and disease free survival (DFS). An intention-to-treat analysis using the Kaplan-Meier method was performed, at 5 and 10 years. p<0.05 was considered statistically significant.

1452 T1N0 breast cancer patients who received ET were identified (Grade 1 subgroup n=661; Grade 2 subgroup n=229). For Grade 1, no statistical difference was found between ET and non-ET in OS (p=0.87) and DFS (p=0.47). Similarly, there was no statistical difference between in OS in Grade 2 (p=0.09) but statistical significance was found for DFS (10 year survival was 69% for non-ET vs 78% for ET; p=0.04). The numbers needed to treat for grade 1 and grade 2 were 159 and 15 respectively.

There was no difference in outcome for the Grade 1 estrogen-receptor positive, HER-2 negative breast cancer patients. Further prospective research is required to determine the safety of the de-escalation and omission of adjuvant ET in this group.