Oxidative balance score and risk of prostate cancer: Results from a case-cohort study

Background: Prostate cancer is a disease with a complex etiology. Oxidative stress has been implicated in its pathogenesis; however, few prospective studies have investigated the association between an oxidative stress/balance score and risk of prostate cancer. Methods: We investigated associations between an oxidative balance score, calculated as the summation of individual scores obtained from five pro-oxidative and eight anti-oxidative exposures, as well as each individual constituent of the score and risks of prostate cancer overall, and by clinical characteristics, in a case-cohort study (661 cases and 1864 subcohort) nested within the Canadian Study of Diet, Lifestyle, and Health cohort. Men in the lowest quintiles of each pro-oxidant exposure received a score of four (the highest score), while those in the highest quintile received a score of zero (the lowest score). In contrast, scoring for all anti-oxidants was performed in the opposite way. Total oxidative balance score was calculated by summating all individual scores of pro- and anti-oxidative variables, with higher values indicating a higher antioxidant status. Results: The average oxidative balance score was similar between prostate cancer cases and men in the subcohort: 25.2 and 25.3, respectively. There was no association between oxidative balance score and overall risk of prostate cancer with hazard ratios (HRs) of 1.00, 1.02, 1.03, 0.97 and 1.01 for increasing quintiles of the score (p-trend = 0.71). There were also no associations for non-advanced or advanced disease, or when analysis was restricted to incident cases that arose after two years of follow-up (n = 508). In general constituents of the score were not associated with prostate cancer, except for red meat intake (HR = 1.44; 95%CI 1.06-1.95 comparing Q5 vs. Q1) and lycopene (HRs of 0.7-0.8 for increasing quintiles). Conclusion: Our findings do not support an association between oxidative balance score and risks of overall prostate cancer or advanced disease.