De‐escalation of five‐year adjuvant endocrine therapy in patients with estrogen receptor‐low positive (immunohistochemistry staining 1%‐10%) breast cancer: Propensity‐matched analysis from a prospectively maintained cohort

• Published in: Cancer 2022-05, Vol.128 (9), p.1748-1756
• Main Authors: Cai, Yu‐Wen, Shao, Zhi‐Ming, Yu, Ke‐Da
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents, Hormonal - therapeutic use; Breast cancer; Breast Neoplasms - therapy; Chemotherapy, Adjuvant; Confidence intervals; Endocrine therapy; estrogen receptor low‐positive; Estrogen receptors; Estrogens; Female; Humans; Immunohistochemistry; Multivariate analysis; Oncology; Original; Patients; Receptors; Receptors, Estrogen - analysis; Regression analysis; short‐term; Staining and Labeling; Statistical analysis; Statistical methods; Subgroups; Survival; Therapy
• ISSN: 0008-543X; 1097-0142
• DOI: 10.1002/cncr.34155

Background The standard 5 years of endocrine therapy has demonstrated additional benefits compared with short‐term (2‐3 years) treatment in patients with estrogen receptor (ER)‐positive breast cancer; however, data specific to ER‐low positive breast cancer (1%‐10% by immunohistochemistry) are limited, and it is unclear whether long‐term treatment is still necessary for this subgroup. Methods The authors used the prospectively maintained Breast Surgery Database of Fudan University Shanghai Cancer Center for this propensity‐matched analysis. The primary end point was disease‐free survival. Multivariate Cox regression analysis and propensity score‐matching methods were used to minimize bias. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated. All statistics were 2‐sided. Results From 2012 to 2017, 22,768 consecutive women had pathologically confirmed, early stage breast cancer, and 1013 (4.45%) were identified with ER‐low positive disease. Among these, 634 patients met the inclusion criteria and were divided into 3 groups: those who received no endocrine therapy (n = 89), those who received 2 to 3 years of endocrine therapy (n = 185), and those who received approximately 5 years of endocrine therapy (n = 360). At a median follow‐up of 65 months, there was no significant difference in disease‐free survival between patients who received 2 to 3 years and 5 years of endocrine therapy (HR, 0.82; 95% CI, 0.51‐1.33; P = .43). The findings were consistent after multivariate Cox analysis of the propensity score‐matched samples (5 vs 2‐3 years of treatment: HR, 0.74; 95% CI, 0.41‐1.31; P = .30). Conclusions Short‐term endocrine therapy for 2 to 3 years might be an alternative for patients who have ER‐low positive breast cancer instead of the standard 5 years of treatment. Short‐term endocrine therapy for 2 to 3 years might be an alternative for patients who have estrogen receptor‐low positive breast cancer instead of the standard 5 years. More extensive studies and translational research on identifying endocrine‐sensitive cases within this population are still needed.