SAN ANTONIO — Inadequate calcium and vitamin D intake—and outright deficiencies—are even more common among breast cancer patients than in the general population, according to studies presented at the annual breast cancer symposium sponsored by the Cancer Therapy and Research Center.
This is particularly unwelcome because women with a history of breast cancer are at elevated risk for skeletal problems due to treatments that induce early menopause. The breast cancer population is also seeing rapidly rising adjuvant use of aromatase inhibitors, a class of drugs that can accelerate bone mineral loss.
Rachel S. Zinaman, a dietitian at Memorial Sloan-Kettering Cancer Center, New York City, noted that 2003 American Society of Clinical Oncology guidelines call for physicians to make screening for and treatment of osteoporosis in breast cancer patients a greater priority. She said it's time for physicians to step up and implement programs to increase breast cancer patients' awareness of the importance of calcium and vitamin D to bone health.
The increased vulnerability of breast cancer patients to calcium and vitamin D deficiencies was underscored by her retrospective chart review of 100 consecutive patients with early-stage breast cancer. The most disturbing finding was that only 10% of the women consumed the recommended daily minimum of 1,000 mg of calcium and 400 U of vitamin D. Indeed, 63% of the women had no significant dietary calcium intake at all, according to Ms. Zinaman.
That's even worse than in the United States at large. A National Institutes of Health consensus conference has concluded that 50%–60% of the older general population meets the established recommended daily intakes of calcium and vitamin D.
In a separate presentation, Marie E. Taylor, M.D., reported finding vitamin D deficiency in fully two-thirds of 233 patients with a current or past diagnosis of breast cancer who presented with a complaint of moderate to severe generalized musculoskeletal discomfort and stiffness with or without localized musculoskeletal symptoms.
The prevalence of vitamin D deficiency as defined by a serum 25-OH vitamin D level below 30 ng/mL varied by race. It was 57% among 162 white patients—but 91% among African Americans, said Dr. Taylor of Washington University, St. Louis.
A total of 65% of the women were hyperparathyroid as defined by a parathyroid hormone level in excess of 72 pg/mL.
Dr. Taylor speculated that the use of aromatase inhibitors may enhance vitamin D requirements and exacerbate a background vitamin D deficiency, resulting in the clinical symptoms of osteomalacia. She and her coinvestigators have prescribed vitamin D for the deficient women in her study cohort and are now following them to see if this leads to symptomatic improvement and better tolerance of adjuvant therapy.
The vitamin D replacement regimen they are using consists of 50,000 U of 25-OH vitamin D once weekly for 8–12 weeks, then cutting back to once every 2 weeks as maintenance therapy. This is coupled with the standard dietary recommendations for calcium and vitamin D intake via food sources and over-the-counter supplements.