TOENAIL TRACE-ELEMENT LEVELS AND BREAST-CANCER - A PROSPECTIVE-STUDY

The associations between toenail levels of five trace elements and bre ast cancer risk were studied among a cohort of 62,641 US women who pro vided toenail clippings and were free from diagnosed breast cancer in 1982. Among 433 cases of breast cancer identified during 4 years of fo llow-up and their matched controls, the odds ratios comparing the high est with the lowest quintiles and adjusted for established breast canc er risk factors were as follows: for arsenic, 1.12 (95% confidence int erval (CI) 0.66-1.91); for copper, 0.91 (95% CI 0.59-1.42); for chromi um, 0.96 (95% CI 0.61-1.52); for iron, 0.89 (95% CI 0.56-1.40); and fo r zinc, 1.09 (95% CI 0.70-1.70). Among postmenopausal women, a margina lly significant positive association was observed between toenail chro mium levels and breast cancer risk (odds ratio = 1.71, 95% CI 0.87-3.3 5) (p for trend = 0.07). However, the association between chromium and breast cancer risk was inverse among premenopausal women. Although da ta on the validity of toenail levels of certain of these elements are limited, these results do not provide evidence for an important effect of arsenic, copper, chromium, iron, or zinc on breast cancer risk.