Disease-free survival (DFS) in patients with estrogen receptor (ER)-low positive breast cancer who received endocrine therapy for 2 to 3 years was similar to DFS in patients who received endocrine therapy for approximately 5 years. These study results, reported in the journal Cancer, support use of short-term endocrine therapy in ER-low positive breast cancer. 

Patients with ER-positive breast cancer, defined as ER expression of ≥10% detected through immunohistochemistry, are typically treated with endocrine therapy. However, the same treatment guidelines are used for breast cancer with ER-low positive status, defined as ER expression of 1% to 10%. Optimal treatment for this group, including duration of endocrine therapy, has been unclear.

This study was a prospective analysis of patients registered with the Breast Surgery Database of Fudan University Shanghai Cancer Center in Shanghai, China, and whose cancer diagnoses occurred between 2012 and 2017. The patients were categorized into 3 groups based on treatment: no endocrine therapy, short-term (2 to 3 years) endocrine therapy, and standard (5 years) endocrine therapy. Disease-free survival was the primary study endpoint.


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Among 22,768 women with confirmed early-stage breast cancer, 1013 patients (4.45%) had ER-low positive status, with 634 patients meeting criteria for inclusion in this analysis. Of these, 89 patients were not treated with endocrine therapy, 185 patients were treated with short-term endocrine therapy, and 360 patients were treated with standard endocrine therapy.

Median follow-up was 65 months (IQR, 44 to 72 months), and 5-year DFS was 85.3% for the overall study population. Five-year DFS was 78.3% for patients who did not receive endocrine therapy, 84.2% for those receiving short-term endocrine therapy, and 87.7% for those receiving standard endocrine therapy. 

In a multivariate analysis, no significant difference in DFS was noted between patients receiving endocrine therapy for 5 years and those receiving it for 2 to 3 years (hazard ratio [HR], 0.77; 95% CI, 0.47-1.26; P =.30). Propensity score matching produced similar results for these 2 groups (HR, 0.74; 95% CI, 0.41-1.31; P =.30). Short-term endocrine therapy reportedly did not compromise overall survival. 

“[O]ur results support the consideration of short-term endocrine therapy for 2 to 3 years for the treatment of ER-low positive early breast cancer,” the researchers concluded. However, they indicated more research is warranted.

Reference

Cai YW, Shao ZM, Yu KD. 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. Cancer. Published online February 25, 2022. doi:10.1002/cncr.34155