a1 Department of Epidemiology University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
a2 Department of Orthopedic Surgery University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
a3 National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
a4 Office of Cancer Prevention and Control, Duke University Medical Center, Durham, NC 27710, USA
Objective To determine if blood levels of 25-hydroxyvitamin D (25-D) or its active metabolite, 1,25-dihydroxyvitamin D (1,25-D), are lower in women at the time of first diagnosis of breast cancer than in comparable women without breast cancer.
Design This was a clinic-based case–control study with controls frequency-matched to cases on race, age, clinic and month of blood drawing.
Setting University-based breast referral clinics.
Subjects One hundred and fifty-six women with histologically documented adenocarcinoma of the breast and 184 breast clinic controls.
Results There were significant mean differences in 1,25-D levels (pmol ml−1) between breast cancer cases and controls; white cases had lower 1,25-D levels than white controls (mean difference ± SE: −11.08 ± 0.76), and black cases had higher 1,25-D levels than black controls (mean difference ± SE: 4.54 ± 2.14), although the number of black women in the study was small. After adjustment for age, assay batch, month of blood draw, clinic and sample storage time, the odds ratio (95% confidence interval, CI) for lowest relative to highest quartile was 5.2 (95% CI 2.1, 12.8) for white cases and controls. The association in white women was stronger in women above the median age of 54 than in younger women, 4.7 (95% CI 2.1, 10.2) vs. 1.5 (95% CI 0.7, 3.0). There were no case–control differences in 25-D levels in either group.
Conclusions These data are consistent with a protective effect of 1,25-D for breast cancer in white women.
(Received July 25 1998)
(Accepted February 01 1999)