The aim of the study was to evaluate the rate of and risk factors for low pretreatment vitamin D (VitD) levels in postmenopausal breast cancer (BC) women, compared with postmenopausal women without BC.
A cross-sectional clinical study was conducted to compare 209 women with BC (case group) to 418 women without BC (control group), age range: 45 to 75 years. The case group consisted of women diagnosed with BC, amenorrhea ≥12 months, aged ≥45 years, without use of medication or clinical conditions that might interfere with VitD levels. The control group consisted of women with amenorrhea ≥12 months, aged ≥45 years, without BC. The groups were matched for age and time since menopause, at a case: control ratio of 1:2. Serum 25-hydroxyvitamin-D [25(OH)D] concentration was measured in all women 10 to 20 days after BC diagnosis and before the proposed treatment. Serum levels ≥30 ng/mL were defined as sufficient. The Student's t test or gamma distribution, χ2 test, and logistic regression (odds ratio, OR) were used for statistical analysis.
The BC group had a higher body mass index (BMI) and higher percentage of obesity than the control group (57.4% vs 40.2%, P < 0.0001). In addition, rates of insufficient (20-29 ng/mL) and deficient (<20 ng/mL) 25(OH)D levels were higher in BC patients than in controls (55.6% vs 49.3%, P = 0.039 and 26.2% vs 20.3%, P = 0.018), respectively. In risk analysis (adjusted for age, time since menopause, and BMI), BC patients had a 1.5-fold higher risk of developing low VitD levels (OR = 1.52, 95% CI, 1.04-2.22, P = 0.029) than women without BC.
Postmenopausal women had an increased risk of VitD deficiency at the time of BC diagnosis, associated with a higher rate of obesity, than women of the same age group without cancer.
From the Department of Gynecology and Obstetrics, Botucatu Medical School, Sao Paulo State University (UNESP), Sao Paulo, Brazil.
Address correspondence to: Eliana A.P. Nahas, MD, PhD, Department of Gynecology and Obstetrics, Botucatu Medical School, Sao Paulo State University (UNESP), Distrito de Rubião Júnior s/n, 18618-970 Botucatu, SP, Brazil. E-mail: email@example.com
Received 21 May, 2018
Revised 14 August, 2018
Accepted 14 August, 2018
Financial disclosure/conflicts of interest: None reported.