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Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study.
Breast Cancer Res Treat 2009; 118(2):395-405BC

Abstract

Soy isoflavones, structurally similar to endogenous estrogens, may affect breast cancer through both hormonally mediated and non-hormonally related mechanisms. Although the effects of soy are not well understood, some breast cancer survivors increase their soy intake post-diagnosis in attempt to improve their prognosis. Therefore, we examined the role of soy isoflavone intake and the risk of breast cancer recurrence by hormone receptor status, menopausal status, and tamoxifen therapy. A cohort of 1,954 female breast cancer survivors, diagnosed during 1997-2000, was prospectively followed for 6.31 years and 282 breast cancer recurrences were ascertained. Isoflavone intake was assessed by mailing modified Block and supplemental soy food frequency questionnaires to participants, on average 23 months post-diagnosis. Risk of breast cancer recurrence, measured by hazard ratios (HR) and 95% confidence intervals (CI), was estimated using multivariable delayed entry Cox proportional hazards models. Suggestive trends for a reduced risk of cancer recurrence were observed with increasing quintiles of daidzein and glycetin intake compared to no intake among postmenopausal women (P for trend: P = 0.08 for daidzein, P = 0.06 for glycetin) and among tamoxifen users (P = 0.10 for daidzein, P = 0.05 for glycetin). Among postmenopausal women treated with tamoxifen, there was an approximately 60% reduction in breast cancer recurrence comparing the highest to the lowest daidzein intakes (>1,453 vs. <7.7 microg/day; HR, 0.48; 95% CI, 0.21-0.79, P = 0.008). Soy isoflavones consumed at levels comparable to those in Asian populations may reduce the risk of cancer recurrence in women receiving tamoxifen therapy and moreover, appears not to interfere with tamoxifen efficacy. Further confirmation is required in other large prospective studies before recommendations regarding soy intake can be issued to breast cancer survivors.

Authors+Show Affiliations

Department of Epidemiology, University of California, Berkeley, CA, USA. neela@berkeley.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19221874

Citation

Guha, Neela, et al. "Soy Isoflavones and Risk of Cancer Recurrence in a Cohort of Breast Cancer Survivors: the Life After Cancer Epidemiology Study." Breast Cancer Research and Treatment, vol. 118, no. 2, 2009, pp. 395-405.
Guha N, Kwan ML, Quesenberry CP, et al. Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study. Breast Cancer Res Treat. 2009;118(2):395-405.
Guha, N., Kwan, M. L., Quesenberry, C. P., Weltzien, E. K., Castillo, A. L., & Caan, B. J. (2009). Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study. Breast Cancer Research and Treatment, 118(2), pp. 395-405. doi:10.1007/s10549-009-0321-5.
Guha N, et al. Soy Isoflavones and Risk of Cancer Recurrence in a Cohort of Breast Cancer Survivors: the Life After Cancer Epidemiology Study. Breast Cancer Res Treat. 2009;118(2):395-405. PubMed PMID: 19221874.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study. AU - Guha,Neela, AU - Kwan,Marilyn L, AU - Quesenberry,Charles P,Jr AU - Weltzien,Erin K, AU - Castillo,Adrienne L, AU - Caan,Bette J, Y1 - 2009/02/17/ PY - 2009/01/15/received PY - 2009/01/15/accepted PY - 2009/2/18/entrez PY - 2009/2/18/pubmed PY - 2009/12/24/medline SP - 395 EP - 405 JF - Breast cancer research and treatment JO - Breast Cancer Res. Treat. VL - 118 IS - 2 N2 - Soy isoflavones, structurally similar to endogenous estrogens, may affect breast cancer through both hormonally mediated and non-hormonally related mechanisms. Although the effects of soy are not well understood, some breast cancer survivors increase their soy intake post-diagnosis in attempt to improve their prognosis. Therefore, we examined the role of soy isoflavone intake and the risk of breast cancer recurrence by hormone receptor status, menopausal status, and tamoxifen therapy. A cohort of 1,954 female breast cancer survivors, diagnosed during 1997-2000, was prospectively followed for 6.31 years and 282 breast cancer recurrences were ascertained. Isoflavone intake was assessed by mailing modified Block and supplemental soy food frequency questionnaires to participants, on average 23 months post-diagnosis. Risk of breast cancer recurrence, measured by hazard ratios (HR) and 95% confidence intervals (CI), was estimated using multivariable delayed entry Cox proportional hazards models. Suggestive trends for a reduced risk of cancer recurrence were observed with increasing quintiles of daidzein and glycetin intake compared to no intake among postmenopausal women (P for trend: P = 0.08 for daidzein, P = 0.06 for glycetin) and among tamoxifen users (P = 0.10 for daidzein, P = 0.05 for glycetin). Among postmenopausal women treated with tamoxifen, there was an approximately 60% reduction in breast cancer recurrence comparing the highest to the lowest daidzein intakes (>1,453 vs. <7.7 microg/day; HR, 0.48; 95% CI, 0.21-0.79, P = 0.008). Soy isoflavones consumed at levels comparable to those in Asian populations may reduce the risk of cancer recurrence in women receiving tamoxifen therapy and moreover, appears not to interfere with tamoxifen efficacy. Further confirmation is required in other large prospective studies before recommendations regarding soy intake can be issued to breast cancer survivors. SN - 1573-7217 UR - https://www.unboundmedicine.com/medline/citation/19221874/Soy_isoflavones_and_risk_of_cancer_recurrence_in_a_cohort_of_breast_cancer_survivors:_the_Life_After_Cancer_Epidemiology_study_ L2 - https://doi.org/10.1007/s10549-009-0321-5 DB - PRIME DP - Unbound Medicine ER -