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Cited by 141Phytoestrogen effects and researchEstrogen and related hormone effectsBreast Cancer Treatment Studies

Effect of soy isoflavones on breast cancer recurrence and death for patients receiving adjuvant endocrine therapy

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Kang, X., Zhang, Q., Wang, S., Huang, X., Jin, S.·2010·Canadian Medical Association Journal
DOI 10.1503/cmaj.091298PMC PMC2988534
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Abstract

BACKGROUND: The intake of soy isoflavones among women with breast cancer has become a public health concern, because these compounds have weak estrogenic effects. There is little clinical evidence about their safety for patients with breast cancer who are receiving adjuvant endocrine therapy. METHODS: For patients who underwent surgery for breast cancer between August 2002 and July 2003 and who were receiving adjuvant endocrine therapy, we examined associations between dietary intake of soy isoflavones and recurrence of breast cancer and death. We measured dietary intake of soy isoflavones at baseline using a validated food frequency questionnaire. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) by means of multivariable Cox proportional hazards regression models. We further stratified the analyses by hormonal receptor status and endocrine therapy. RESULTS: The median follow-up period for the 524 patients in this study was 5.1 years. Among premenopausal patients, the overall death rate (30.6%) was not related to intake of soy isoflavones (HR = 1.05, 95% CI 0.78-1.71 for the highest quartile [> 42.3 mg/day] v. the lowest quartile [< 15.2 mg/day], p for trend = 0.87). Relative to post-menopausal patients in the lowest quartile of soy isoflavone intake, the risk of recurrence for post-menopausal patients in the highest quartile was significantly lower (HR = 0.67, 95% CI 0.54-0.85, p for trend = 0.02). Inverse associations were observed in patients with estrogen and progesterone receptor positive disease and those receiving anastrozole therapy. INTERPRETATION: High dietary intake of soy isoflavones was associated with lower risk of recurrence among post-menopausal patients with breast cancer positive for estrogen and progesterone receptor and those who were receiving anastrozole as endocrine therapy.

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  • Of seven prospective studies examining survival, four (57%) showed protective effects on breast cancer mortality or mortality in breast cancer patients.

    “Of seven studies examining survival [94,96,98,100,101,106,112], four (57%) showed protective effects on breast cancer mortality or mortality in breast cancer patients [94,96,101,112].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [106]

    The Menopausal status section reports no association between soy isoflavone intake and death in postmenopausal patients, with similar results for breast-cancer-specific mortality. The paper reports a lower risk of recurrence, not a protective effect on mortality. Its single cohort also cannot establish the citing sentence’s four-of-seven count. (LLM, conf=0.88)

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  • Two additional prospective survival studies showed no significant effects.

    “Two additional studies showed no significant effects [98,106].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [106]

    The Menopausal status section reports no association between soy isoflavone intake and death, and no association with recurrence or death among premenopausal patients. But it also reports a significantly lower recurrence risk among postmenopausal patients with the highest intake, so describing this study as showing no significant effects is too broad. (LLM, conf=0.88)

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  • Four cohort studies and three RCTs reported no significant differences in treatment outcomes or rates of adverse effects associated with soy use among women receiving tamoxifen therapy.

    “Four cohort studies [100,103,106,112] and three RCTs [128,130,131] reported no significant differences with respect to treatment outcomes or rates of adverse effects associated with use of soy among women who were receiving tamoxifen therapy.”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [106]

    The Results identify this paper as one cohort study, and the Hormonal receptor status and endocrine therapy section reports no statistically significant association between soy intake and recurrence in its postmenopausal tamoxifen subgroup (Figure 1; page unavailable). The paper does not report RCT findings or compare rates of adverse effects associated with soy use, so it supports only part of the cited sentence. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Soy consumption may protect against the development of breast cancer, and less so against breast cancer recurrence and mortality, although this is based on observational data only.

    “Our review suggests that on the contrary, soy consumption may protect against the development of breast cancer [46,75,109,117], and less so, breast cancer recurrence and mortality [106,112], although this is based on observational data only.”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [106]

    The Menopausal status section reports an observational association between higher soy isoflavone intake and lower recurrence risk in postmenopausal patients receiving endocrine therapy. It reports no association with death, including breast-cancer mortality, and no association with recurrence among premenopausal patients. This source is cited for recurrence and mortality, not for the separate claim about breast cancer development. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Of five prospective studies reporting on recurrence, two (40%) showed protective effects.

    “Of five studies reporting on recurrence [97,100,103,106,112], two (40%) showed protective effects [106,112].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [106]

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Authors
Kang, X., Zhang, Q., Wang, S., Huang, X., & Jin, S.
Affiliations
Harbin Medical University (CN)
ORCID
Venue
Canadian Medical Association Journal
Publisher
CMA Impact Inc.
Published
2010-10-18
Volume
182
Issue
17
Pages
1857-1862
ISSN
  • 0820-3946 (ISSN-L)
  • 1488-2329
DOI
10.1503/cmaj.091298
PMC
PMC2988534
OpenAlex
W2171549094
Cited by
141
References
0
Citations by year
2026: 6 · 2025: 7 · 2024: 5 · 2023: 7 · 2022: 5 · 2021: 7 · 2020: 9 · 2019: 7 · 2018: 8 · 2017: 9 · 2016: 9 · 2015: 12 · 2014: 4 · 2013: 13 · 2012: 14
FWCI
9.43
Type
journal article
Language
en
Open access
Locations
  • Canadian Medical Association Journal (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
Harbin Science and Technology Bureau
Topics
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Phytoestrogen effects and research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Estrogen and related hormone effects
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Breast Cancer Treatment Studies
Keywords
soy isoflavones, breast cancer, breast cancer recurrence, breast cancer mortality, adjuvant endocrine therapy, anastrozole, dietary intake, estrogen receptor, progesterone receptor, menopausal status
MeSH terms
Adult, Aged, Breast Neoplasms, Diet, Diet Surveys, Female, Humans, Isoflavones, Menopause, Middle Aged, Recurrence, Multivariate Analysis, Confidence Intervals, Proportional Hazards Models, Chemotherapy, Adjuvant, Antineoplastic Agents, Hormonal, Soy Milk, Soy Foods

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