Calcium metabolism and breast cancer risk

Sammanfattning: Emerging evidence suggests that calcium and its regulating hormones, i.e. vitamin D and parathyroid hormone (PTH), affect breast cancer risk. The associations between serum calcium levels and breast cancer risk, between serum calcium levels and known risk factors of breast cancer, and between serum calcium levels and breast cancer aggressiveness were examined within the Malmö Preventive Project, a population-based cohort comprising 10,902 women. Serum calcium, 25-hydroxyvitamin D (25OHD) and PTH-levels were furthermore examined in relation to breast cancer risk in a nested case-control study comprising 764 breast cancer cases within the Malmö Diet and Cancer Study. Serum calcium levels were positively associated with breast cancer risk in overweight/obese women. In premenopausal women, serum calcium was in one study negatively, and in one study positively, associated with breast cancer. Calcium was positively associated with breast cancer aggressiveness in overweight and/or premenopausal women. Premenopausal status and use of oral contraceptives and hormone-replacement therapy were negatively associated with serum calcium levels. BMI was significantly associated with serum calcium levels, with lean and overweight women having higher calcium levels than women with BMI between 20 and 25. There was a weak, statistically non-significant, inverse association between 25OHD-levels and breast cancer risk. There was no evidence for any relation between PTH-levels and breast cancer. It is concluded that serum calcium is positively associated with breast cancer risk and aggressiveness in overweight women. There may be a weak negative association between vitamin D and breast cancer risk, but this will have to be further examined.