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Abstract: Coffee consumption and risk of lethal and advanced prostate cancer.

Coffee consumption and risk of lethal and advanced prostate cancer. Kathryn M. Wilson1, Julie L. Kasperzyk1, Jennifer R. Stark1, Michael N. Pollak2, Meir J. Sampfer3, Edward Giovannucci1, Lorelei A. Mucci3. 1Harvard School of Public Health, Boston, MA; 2McGill University, Montreal, QC, Canada; 3Channing Laboratory, Brigham and Women’s Hospital/Harvard Medical School, Boston, MA.

Background: Coffee is a commonly consumed beverage which contains many biologically active compounds. It is a major source of caffeine and antioxidants, and it has effects on insulin and glucose metabolism as well as sex hormone levels. This suggests that coffee may have a beneficial effect on risk of prostate cancer; however, this association has not been studied in depth.

Methods: We prospectively investigated the association between coffee intake and prostate cancer risk in the Health Professionals’ Follow-Up Study. From 1986 to 2006, 4975 cases of prostate cancer were identified. Intake of regular and decaffeinated coffee was assessed in 1986 and every four years thereafter. We used Cox proportional hazards models to assess the association between coffee intake and risk of prostate cancer. To investigate possible mechanisms, we used linear regression to examine the cross-sectional association between coffee intake and levels of circulating hormones in blood samples collected between 1993 and 1995 from a subset of men in the cohort.

Results: There was a weak inverse association between total coffee intake and overall prostate cancer risk, with an adjusted relative risk of 0.81 (95% CI: 0.67-0.97, p-value for linear trend=0.08) for men consuming six or more cups of coffee (regular or decaf) per day compared to non-drinkers. The association was stronger for lethal and advanced (fatal, T3b or T4, or N1 or M1) prostate cancers. Compared to non-drinkers, the highest consumers had a relative risk of 0.41 (CI: 0.22-0.77, p-trend=0.02) for lethal cancer and 0.41 (CI: 0.24-0.71, p-trend=0.002) for advanced cancer. The association with lethal and advanced cancers was more pronounced in never smoking men (RR=0.11; CI: 0.02-0.83, p-trend=0.001 for advanced cancer). The inverse association was seen in both the pre-PSA and PSA screening eras.

Results were similar for regular and decaffeinated coffee. For the highest versus lowest groups of intake, the relative risk of advanced cancer was 0.67 (CI: 0.34-1.33, p-trend=0.03) for regular coffee and 0.72 (CI: 0.46-1.13, p- trend=0.03) for decaffeinated coffee. There was an inverse association between caffeine intake and risk of lethal and advanced disease, but this association was weaker than that seen for coffee, and it became non-significant when total coffee intake was also included in the model. Coffee intake was inversely associated with plasma levels of C-peptide (p-trend=0.003) and positively associated with testosterone (p-trend=0.03) and SHBG (p-trend=0.04). Coffee intake was not related to circulating levels of IGF-1, IGFBP3, free testosterone, or estradiol.

Conclusion: The strong inverse association between coffee consumption and risk of lethal and advanced prostate cancers is potentially important and should be confirmed in other populations. The association appears to be related to non-caffeine components of coffee and may be mediated through effects on insulin metabolism and/or sex hormone levels.

(Reprinted from the Frontiers in Cancer Prevention Research conference program)

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