Time-specific impact of trace metals on breast density of adolescent girls in Santiago, Chile

Whether trace metals modify breast density, the strongest predictor for breast cancer, during critical developmental stages such as puberty remains understudied. Our study prospectively evaluated the association between trace metals at Tanner breast stage B1 (n = 291) and at stages both B1 and B4 (n = 253) and breast density at 2 years post-menarche among Chilean girls from the Growth and Obesity Cohort Study. Dual-energy x-ray absorptiometry assessed the volume of dense breast tissue (absolute fibroglandular volume [FGV]) and percent breast density (%FGV). Urine trace metals included arsenic, barium, cadmium, cobalt, cesium, copper, magnesium, manganese, molybdenum, nickel, lead, antimony, selenium, tin, thallium, vanadium, and zinc. At B1, a doubling of thallium concentration resulted in 13.69 cm³ increase in absolute FGV (β: 13.69, 95% confidence interval [CI]: 2.81, 24.52), while a doubling of lead concentration resulted in a 7.76 cm³ decrease in absolute FGV (β: -7.76, 95%CI: -14.71, -0.73). At B4, a doubling of barium concentration was associated with a 10.06 cm³ increase (β: 10.06, 95% CI: 1.44, 18.60), copper concentration with a 12.29 cm³ increase (β: 12.29, 95% CI: 2.78, 21.56), lead concentration with a 9.86 cm³ increase (β: 9.86, 95% CI: 0.73, 18.98), antimony concentration with a 12.97 cm³ increase (β: 12.97, 95% CI: 1.98, 23.79) and vanadium concentration with a 13.14 cm³ increase in absolute FGV (β: 13.14, 95% CI: 2.73, 23.58). Trace metals may affect pubertal breast density at varying developmental stages with implications for increased susceptibility for breast cancer.