The risk between inflammation and the pathogenesis of prostate cancer is well understood, yet proliferative inflammatory atrophy, non-steroidal anti-inflammatory drugs, and dietary compounds have also demonstrated an associative relationship.
The authors in this study hypothesized that omega-6 and trans fatty acids (TFAs) would be positively associated with increased prostate cancer risk, while omega-3 fatty acids would be inversely associated with such risk. Subjects were identified as a case-control study nested within the Prostate Cancer Prevention Trial (PCPT).
All men in this study group were aged 55-84 years with no history of prostate cancer or severe benign prostatic hyperplasia, and with a prostate specific antigen (PSA) level of <= 3.0ng/mL. Throughout the 7 years of the PCPT, men who developed an abnormal digital rectal examination or a finasteride-adjusted PSA level of >=4.0ng/mL were referred for a prostate biopsy to rule out cancer. Non-fasting serum lipid analyses were sampled 3 months prior to randomization of this arm of the study, specifically assaying levels of various components of omega-3 fatty acids (eg, alpha-linolenic acid, eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA]), omega-6 fatty acids (eg, linolenic acid, arachidonic acid), and trans fatty acids.
The authors concluded that no fatty acid components were associated with low-grade prostate cancer risk. DHA was associated with high-grade prostate cancer (Gleason 8 or higher) with and odds ratio of 2.5. However, various TFAs were inversely associated with prostate cancer risk (OR 0.55 and 0.48).
These results are the opposite of what might be expected in that the anti-inflammatory omega-3 fatty acids yielded an increased risk of prostate cancer while higher serum concentrations of the pro-inflammatory omega-6 and TFAs suggested a decreased prostate cancer risk, exactly the contrary to what was hypothesized.
By comparison, The Physicians' Health Study recently discovered inverse associations between serum EPA and DHA with risk of both aggressive and non-aggressive prostate cancers. The European Prospective Investigation into Cancer and Nutrition study revealed that DHA was associated with elevated risks of both low-grade and high-grade prostate cancer.
In conclusion, the authors admit that the pathway(s) of prostate cancer are not completely understood in detail, and that a proposed mechanism for EPA and DHA as carcinogenic agents is not known. Nonetheless, a link between these fatty acids and prostate cancer cannot be claimed, as the complexity of the role of these nutrients across many forms of disease still needs to be elucidated.
Reference: Brasky TM, Till C, White E, et al. Serum phospholipid fatty acids and prostate cancer risk: results from the Prostate Cancer Prevention Trial. Am J Epidemiol 2011; published ahead of print April 24, 2011.