Changes to This Summary (10/10/2014)
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Added text about a 2013 meta-analysis, including four of five cohort studies from a 2004 meta-analysis, two new meta-analyses, and three case-control studies from the previous study plus eight new ones, that reported less convincing evidence for risk reduction; the authors concluded that tomatoes may play a modest role in the prevention of prostate cancer (cited Chen et al. as reference 26).
Added text about an updated 2013 meta-analysis that confirmed the good safety profiles of isoflavones but indicated no significant differences between treated and control groups for prostate-specific antigen (PSA) levels or sex steroid endpoints (cited van Die et al. as reference 22).
Added text to state that another group conducted a randomized placebo-controlled trial to examine the effect of soy isoflavone capsules on localized prostate cancer in 86 men who took the capsules for up to 6 weeks before prostatectomy; changes in serum-free and total testosterone, PSA, and total cholesterol were not different between the two groups, and the investigators noted that the 12 genes involved in cell cycle control and the 9 genes involved in apoptosis were down regulated in the tumor tissues of the isoflavone-treated men, compared with the controls (cited Hamilton-Reeves et al. as reference 32).
Added text to state that in a 2 X 2 factorial design study that investigated soy protein powder and venlafaxine in 120 androgen-deprived men, neither proved effective alone or in combination in decreasing hot flashes, although the number of vasomotor symptoms decreased significantly in all four arms over the 12-week trial; soy protein, but not venlafaxine, produced statistically significant improvements in emotional and functional subscales on quality-of-life instruments (cited Vitolins et al. as reference 40).
Added text about a 2014 study that evaluated calcitriol and a less-calcemic vitamin D analog in an aggressive transgenic adenocarcinoma of the mouse prostate model and found that neither vitamin D analog impacted the rate of development of castration-resistant prostate cancer in mice, whether they were treated before or after castration; however, both vitamin D analogs slowed progression of primary tumors in hormone-intact mice but enhanced distant organ metastases after prolonged treatment (cited Ajibade et al. a reference 8). Also added text to state that this preclinical data supports findings of the 2008 retrospective study of an association between serum vitamin D levels and aggressive prostate cancer (cited Ahn et al. as reference 9).
Added text to state that a 2008 retrospective study of 749 men with prostate cancer diagnosed 1 to 8 years after blood draw and 781 matched controls found higher circulating 25(OH)D concentrations may be associated with increased risk of aggressive disease. Also added text to state that both of these studies were included in a meta-analysis of 21 studies, involving 11,941 cases and 13,870 controls, that found a 17% elevated risk of prostate cancer in men with higher levels of 25(OH)D; one explanation offered for this finding may be a potential detection bias with men from higher socio-economic groups who have higher vitamin D levels and who are more likely to undergo PSA testing, resulting in higher reported incidence rates (cited Xu et al. as reference 17).
Added text to state that serum 25(OH)D levels were obtained from 667 men in Chicago undergoing first prostate biopsy for an elevated PSA or an abnormal digital rectal exam; severe vitamin D deficiency was associated with increased risk of a prostate cancer diagnosis on biopsy among African American men, and severe deficiency was positively associated with higher Gleason score, higher clinical stage, and overall risk category in both white and African American men (cited Murphy et al. as reference 18). Also added text to state that baseline serum 25(OH)D levels obtained in a case-cohort analysis from the Selenium and Vitamin E Cancer Prevention Trial found significantly reduced risks among men who had moderate concentrations compared with men who had lower or higher values (cited Kristal et al. as reference 19).
Added text about a meta-analysis of nine nested case-control studies, representing approximately 370,000 men from several countries, that also found an inverse relationship between alpha-tocopherol levels and prostate cancer risk but in all the men studied rather than limited to a smoking subset; no association was seen with gamma-tocopherol levels. Also added text to state that the risk of prostate cancer decreased by 21% for every 25 mg/L increase in blood alpha-tocopherol level (cited Cui et al. as reference 11).
This summary is written and maintained by the PDQ Cancer Complementary and Alternative Medicine Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ NCI's Comprehensive Cancer Database pages.