Vitamin D and breast cancer.

In addition to its role in calcium homeostasis and bone health, vitamin D has also been reported to have anticancer activities against many cancer types, including breast cancer. The discovery that breast epithelial cells possess the same enzymatic system as the kidney, allowing local manufacture of active vitamin D from circulating precursors, makes the effect of vitamin D in breast cancer biologically plausible. Preclinical and ecologic studies have suggested a role for vitamin D in breast cancer prevention. Inverse associations have also been shown between serum 25-hydroxyvitamin D level (25(OH)D) and breast cancer development, risk for breast cancer recurrence, and mortality in women with early-stage breast cancer. Clinical trials of vitamin D supplementation, however, have yielded inconsistent results. Regardless of whether or not vitamin D helps prevent breast cancer or its recurrence, vitamin D deficiency in the U.S. population is very common, and the adverse impact on bone health, a particular concern for breast cancer survivors, makes it important to understand vitamin D physiology and to recognize and treat vitamin D deficiency. In this review, we discuss vitamin D metabolism and its mechanism of action. We summarize the current evidence of the relationship between vitamin D and breast cancer, highlight ongoing research in this area, and discuss optimal dosing of vitamin D for breast cancer prevention.

Prevention of bone loss by zoledronic acid in premenopausal women undergoing adjuvant chemotherapy persist up to one year following discontinuing treatment.

CONTEXT: Adjuvant chemotherapy is associated with significant reductions in bone mineral density (BMD) in premenopausal women with breast cancer (BC) that is prevented with zoledronic acid (ZA) every 3 months for 1 yr. OBJECTIVE: The aim of the study was to examine the effect on BMD of discontinuing ZA during the subsequent year. DESIGN: We conducted a randomized, double-blind trial. PATIENTS: Premenopausal women (mean age, 42 yr) undergoing adjuvant chemotherapy for BC participated in the study. INTERVENTION: ZA (4 mg iv every 3 months) vs. placebo was administered for 12 months. OUTCOME MEASURES: We measured percentage change in BMD and bone turnover markers at 12 and 24 months (1 yr after last infusion). RESULTS: Of 101 women randomized, 85 completed 12-month and 62 completed 24-month evaluations. In the placebo group, serum C-telopeptide (CTX) increased progressively over the first 12 months, returned toward baseline but remained significantly above baseline by 24 months. Lumbar spine BMD decreased from baseline by 5.5% at 12 and 6.3% at 24 months. Similarly, by 24 months, total hip and femoral neck BMD declined by 2.6 and 2.4%, respectively. In ZA patients, BMD remained stable (P < 0.0001 compared to placebo). Serum CTX declined significantly by 6 months, but returned to baseline by 12 months, remaining there at 24 months. CONCLUSIONS: Premenopausal women receiving chemotherapy for BC sustained significant bone loss during the first year, without recovery during the second year. ZA effectively prevented bone loss during the first year of chemotherapy. BMD remained stable 1 yr after completion of ZA. Serum CTX increased significantly by 12 and 24 months. More frequent administration may be required to suppress bone resorption in this patient population.