Article
Serum enterolactone and prognosis of postmenopausal breast cancer
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Published: | September 20, 2011 |
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Background: Lignans – plant-derived compounds with estrogen-dependent and independent anti-carcinogenic properties – have been associated with postmenopausal breast cancer risk, but data is limited regarding their effect on survival. Dietary lignans are metabolized to enterolignans, which are subsequently absorbed and become bioavailable.
Methods: We assessed prognosis of 1,140 postmenopausal breast cancer patients aged 50-74 years and diagnosed between 2002 and 2005. Vital status through the end of 2009 was ascertained via local population registries and deaths were verified by death certificates. Information on recurrences and secondary tumors was verified by clinical records/attending physicians. Associations of post-diagnostic serum enterolactone (a biomarker for dietary lignans) with overall survival (OS) and distant disease-free survival (DDFS) were assessed using Cox proportional hazards models stratified by age at diagnosis and adjusted for prognostic factors.
Results: Median enterolactone levels for deceased and non-deceased patients were 17.0 and 21.4 nmol/L, respectively. During a median of 5.8 years follow-up after diagnosis, 162 total deaths were confirmed. Higher serum enterolactone levels were associated with significantly reduced hazard ratios (HR) for OS (HR per 10 nmol/L increment=0.94, p=0.04; HR for the highest quartile=0.58, 95% confidence interval (CI)=0.34-0.99). For DDFS, HR was 0.94 per 10 nmol/L increment, p=0.08, and 0.62 for the highest quartile, 95% CI=0.35-1.09. Although there was no significant heterogeneity by estrogen receptor (ER) status (p=0.09), the highest quartile of serum enterolactone was associated with a significantly better OS only for ER-negative tumors (HR=0.27, 95% CI=0.08-0.87).
Conclusion: Postmenopausal breast cancer cases with high serum enterolactone levels may have a better survival.