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More Evidence Links Vitamin D Deficiency to Worse Outcomes in Breast Cancer

March 2013, Highlights

More evidence is accumulating that vitamin D levels play a role in breast cancer outcomes. Investigators from the United Kingdom reported that postmenopausal women with sufficient vitamin D levels were significantly less likely to develop bone metastases when taking zoledronic acid (Zometa) compared with women with lower vitamin D levels.

“Patients with a sufficient level of vitamin D had a better prognosis,” said Robert Coleman, MBBS, MD, FRCP, Professor, Department of Oncology, the University of Sheffield, England, and an Associate Director of the National Institute for Health Research Cancer Research Network in the United Kingdom. He called the findings “quite surprising.”

However, markers of bone turnover were not associated with risk, Dr Coleman added.

The findings came from an analysis of tissue samples from 872 participants of the large AZURE trial, which evaluated the efficacy of zoledronic acid in 3360 patients with early breast cancer. This subgroup analysis included 606 premenopausal women and 266 postmenopausal women.

AZURE showed little benefit in adding zoledronic acid to chemotherapy, but in a prespecified analysis, the postmenopausal women had a significantly lower risk of recurrence, in the bone and in distant sites, compared with premenopausal women. The current investigation sought to explore this, and looked at baseline levels of 2 markers of bone turnover (CTX and P1NP) as well as 25-hydroxyvitamin (25[OH])D as a marker of bone and general health.

The 25(OH)D level was deemed “insufficient” at ?30 ng/mg and “sufficient” above this level. A striking finding was that only 10.3% of women had sufficient vitamin D levels, Dr Coleman reported.

Vitamin D Level Linked to Recurrence

Although neither of the 2 bone turnover markers predicted outcomes, there were “quite surprising differ­ences” in recurrence based on 25(OH)D levels, he said.

A low vitamin D level predicted the development of bone metastases, with a hazard ratio (HR) of 0.11 (P = .025). A low vitamin D level appeared to predict for distant recurrence as well, with an HR of 0.56, but this did not reach statistical significance.

Dr Coleman suggested that the findings have clinical implications. “Clinicians should be measuring vitamin D [and] replenishing it appropriately,” he noted. “But whether vitamin D as an intervention will change outcome, I don’t know.”

Carol A. Lange, PhD, coleader of the Women’s Cancer Research Pro­gram, Professor of the Departments of Medicine and Pharmacology, Tickle Family Land Grant Endowed Chair in Breast Cancer Research, and Director, Cancer Biology Training Grant of the University of Minnesota, Minneapolis, who moderated the session, agreed that “it’s a really good idea” to keep vitamin D levels in the sufficient range, noting that this is an inexpensive and apparently safe intervention.

Current studies are attempting to further elucidate the mechanism underlying vitamin D’s potential antitumor effects, Dr Lange said.—CH

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