Urinary 6-sulfatoxymelatonin Levels and Prostate Cancer Risk among Men in the Multiethnic Cohort

Background: The circadian hormone melatonin has anticancer properties, and prior studies suggest a positive association between low melatonin and prostate cancer risk. The purpose of this study was to examine urinary melatonin levels and prostate cancer in a racially/ethnically diverse cohort. Methods: We conducted a nested case-control study, including 1,263 prostate cancer cases and 2,346 controls, sampled from participants in the Multiethnic Cohort Study with prediagnostic urine samples assayed for 6-sulfatoxymelatonin, the primary melatonin metabolite. Conditional logistic regression was used to examine the association between melatonin levels and the development of prostate cancer outcomes (all incident cases, advanced, lethal, high-grade, and aggressive), overall and by race/ethnicity. Results: Among 1,263 cases, 135 were advanced stage, 101 were lethal cases, and 282 were high-grade disease. Median melatonin levels were similar in controls [17.12 ng/mL; interquartile range (IQR), 19.78) and cases (17.93 ng/mL; IQR, 19.76), and we found no significant association between urinary melatonin levels and prostate cancer risk overall or in any clinical or racial subgroup. Conclusions: In this diverse cohort, there was no significant association between melatonin and any prostate cancer outcome, nor were there any differences by racial/ethnic group. Impact: These results do not support a strong association between melatonin levels and risk of prostate cancer.