Rodrigo Arrangoiz MS, MD, FACS, FSSO

New Research Alert: ER-Low Breast Cancer & Endocrine Therapy (2026)

Liu et al. Breast Cancer Res Treat. Published Jan 6, 2026. 

🔬 Key Focus

This study evaluated outcomes and benefits of endocrine therapy (ET) in early breast cancer patients with low estrogen receptor (ER) expression (1%–10%) compared to ER-high and ER-negative cancers. 

📊 Major Findings

🧬 ER-Low Phenotype Is Distinct

ER-low (~4.4% of cases) behaves more like ER-negative disease in HER2-negative patients. Worse breast cancer-free survival compared to ER-high. Similar risk to triple-negative disease in HER2-negative subgroup. 

💊 Endocrine Therapy Benefit Varies by Subtype

📍 HER2-Negative ER-Low:

✔ ET significantly reduced locoregional recurrence & distant metastasis

✔ Improved breast cancer–free survival (BCFS) 

📍 HER2-Positive ER-Low:

❌ No clear survival or BCFS benefit from ET observed 

🧠 Clinical Implications

✅ Consider ET in HER2-negative, ER-low early breast cancer

⚠️ The benefit of ET in HER2-positive ER-low remains uncertain

🧪 ER-low shouldn’t be treated the same as classical ER-high luminal tumors 

📌 Why This Matters

ER-low tumors are being increasingly recognized as a biologically unique subgroup. This research supports more nuanced treatment planning, particularly regarding the value of endocrine therapy based on HER2 status.  

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Published by Rodrigo Arrangoiz MS, MD, FACS, FSSO

My name is Rodrigo Arrangoiz I am a breast surgeon/ thyroid surgeon / parathyroid surgeon / head and neck surgeon / surgical oncologist that works at Center for Advanced Surgical Oncology in Miami, Florida. I was trained as a surgeon at Michigan State University from (2005 to 2010) where I was a chief resident in 2010. My surgical oncology and head and neck training was performed at the Fox Chase Cancer Center in Philadelphia from 2010 to 2012. At the same time I underwent a masters in science (Clinical research for health professionals) at the University of Drexel. Through the International Federation of Head and Neck Societies / Memorial Sloan Kettering Cancer Center I performed a two year head and neck surgery and oncology / endocrine fellowship that ended in 2016. Mi nombre es Rodrigo Arrangoiz, soy cirujano oncólogo / cirujano de tumores de cabeza y cuello / cirujano endocrino que trabaja Center for Advanced Surgical Oncology en Miami, Florida. Fui entrenado como cirujano en Michigan State University (2005 a 2010 ) donde fui jefe de residentes en 2010. Mi formación en oncología quirúrgica y e n tumores de cabeza y cuello se realizó en el Fox Chase Cancer Center en Filadelfia de 2010 a 2012. Al mismo tiempo, me sometí a una maestría en ciencias (investigación clínica para profesionales de la salud) en la Universidad de Drexel. A través de la Federación Internacional de Sociedades de Cabeza y Cuello / Memorial Sloan Kettering Cancer Center realicé una sub especialidad en cirugía de cabeza y cuello / cirugia endocrina de dos años que terminó en 2016.

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