Oral herbal medicine for breast cancer-related symptoms: an evidence map of systematic reviews.

BACKGROUND: Breast cancer remains the most commonly diagnosed malignancy in women worldwide. While the use of herbal medicine as a complementary approach has expanded, the existing literature is highly heterogeneous, and a comprehensive overview mapping the research landscape is lacking. OBJECTIVE: This evidence map identifies the evidence and research gaps in herbal medicine for breast cancer. METHODS: Ten electronic databases were systematically searched from inception to 30 April 2025. Systematic reviews (SRs) and meta-analyses of randomized controlled trials (RCTs) evaluating herbal medicine for breast cancer patients were included. Two reviewers independently screened the literature, selected eligible studies, and extracted data, and the methodological quality of the included reviews was assessed using AMSTAR 2. The included SRs were stratified into two groups based on the timing of herbal medicine administration ("Undergoing treatment" and "Mixed / Both phase") and visualized as a bubble chart using custom HTML5 and Scalable Vector Graphics (SVG) code, developed with the assistance of Claude (Claude sonnet 4.6, Anthropic). In this map, the treatment phase and clinical condition are plotted on the x-axis and 12 predefined outcome domains on the y-axis, with bubble color indicating the direction of effect, and bubble size representing the number of SRs. RESULTS: A total of 31 SRs were included, published between 2012 and 2025. The included reviews were more concentrated in the "Undergoing treatment" phase (n = 27) than in the "Mixed / Both phase" (n = 4). Most SRs addressed non-symptom-specific chemotherapy outcomes (n = 13), followed by menopausal-like symptoms (n = 4), with predominantly positive findings. According to AMSTAR 2, 28 SRs (90.3%) were rated as "Critically Low" quality and 3 SRs (9.7%) as "Low" quality, with critical deficits in protocol registration and risk of bias consideration. CONCLUSION: This evidence map provides the first comprehensive visual overview of SRs on herbal medicine for breast cancer. While clustering around treatment-related symptom management, the methodological quality is consistently low. Future research must prioritize high-quality trials in under-investigated domains and long-term, patient-centered outcomes, using standardized protocols and rigorous adherence to international reporting guidelines. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD420261330650, identifier CRD420261330650.