Urinary Levels of Melatonin and Risk of Postmenopausal Breast Cancer: Women's Health Initiative Observational Cohort
Couplée aux données de la cohorte observationnelle "Women's Health Initiative" et portant sur 258 cas et 515 témoins, cette étude évalue l'association entre le niveau de mélatonine contenu dans les urines et le risque de cancer du sein après la ménopause
Background: Results from prospective studies on the association between urinary levels of melatonin and risk of postmenopausal breast cancer have been mixed. Several although not all studies have found lower urinary levels of melatonin in women who developed breast cancer compared to cancer-free women. Methods: We examined the association between urinary levels of melatonin and breast cancer risk in postmenopausal women in a case-control study nested in the Women's Health Initiative Observational Cohort. Levels of 6-sulfatoxymelatonin were measured in first morning voids from 258 women who later developed breast cancer and from 515 matched controls. Multivariable conditional logistic regression was used to calculate odds ratios and 95% confidence intervals. Results: Fully adjusted risk estimates of breast cancer, relative to the lowest quartile level of creatinine-adjusted melatonin, were 1.07 (95% CI 0.67-1.71), 1.26 (95% CI 0.79-2.01), and 1.25 (95% CI 0.78-2.02) for women in the second, third and highest quartile [p for trend =.27]. Comparable results for cases diagnosed less than four years after urinary collection and matched controls were 1.0, 1.25 (95%CI 0.51-3.06, 1.85 (95%CI 0.75-4.57), and 1.94 (95%CI 0.75-5.03) [p for trend = 0.11]. Melatonin levels and breast cancer were not associated in cases diagnosed four or more years after urinary collection and matched controls [p for trend = 0.89]. Conclusions: We found no evidence that higher urinary levels of melatonin are inversely associated with breast cancer risk in postmenopausal women. Impact: Accumulating discrepancies in results across studies warrant further exploration.