PT - JOURNAL ARTICLE AU - Xinmei Kang AU - Qingyuan Zhang AU - Shuhuai Wang AU - Xu Huang AU - Shi Jin TI - Effect of soy isoflavones on breast cancer recurrence and death for patients receiving adjuvant endocrine therapy AID - 10.1503/cmaj.091298 DP - 2010 Nov 23 TA - Canadian Medical Association Journal PG - 1857--1862 VI - 182 IP - 17 4099 - http://www.cmaj.ca/content/182/17/1857.short 4100 - http://www.cmaj.ca/content/182/17/1857.full SO - CMAJ2010 Nov 23; 182 AB - 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.