SynthesisThe oncologist2026
Association between endocrine therapy and survival outcomes in estrogen receptor-low breast cancer: a systematic review and meta-analysis.
Synthesis in The oncologist, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
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Authors and funding
5 authors.
Funding
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Abstract
backgroundThe clinical significance of endocrine therapy (ET) in patients with estrogen receptor-low (ER-low, 1%-10%) breast cancer remains uncertain. Increasing evidence suggests that these tumors differ biologically from typical hormone receptor-positive cancers, raising questions about the true benefit of ET in this subgroup.
methodsThis systematic review and meta-analysis was conducted in accordance with the PRISMA 2020 guidelines. PubMed, Embase, the Cochrane Library, and Web of Science were searched from inception to July 1, 2025. Hazard ratios (HRs) with corresponding 95% CIs for time-to-event outcomes were extracted directly or estimated from Kaplan-Meier curves when not explicitly reported. Pooled analyses were performed using random-effects models to account for between-study heterogeneity. The protocol was registered in PROSPERO (CRD420251055521).
resultsA total of 6 retrospective observational studies involving 8765 patients with estrogen receptor-low breast cancer were included. Endocrine therapy was associated with improved overall survival (OS) (HR 0.81, 95% CI 0.69-0.95; P = .01; I2 = 0%) and disease-free survival (DFS) (HR 0.64, 95% CI 0.45-0.90; P = .01; I2 = 0%).
conclusionsEndocrine therapy was associated with improved OS and DFS in patients with estrogen receptor-low breast cancer. These findings suggest that estrogen receptor-low breast cancer should not be uniformly considered endocrine-insensitive and that routine omission of endocrine therapy should be approached cautiously. Given that the available evidence is derived from retrospective observational studies, further prospective studies are needed to identify patients most likely to benefit from endocrine therapy.
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