Study Shows Increased Risk for Aggressive Breast Cancer in Women With Low Vitamin D Levels
By Salynn Boyles
WebMD Health News
Reviewed by Laura J. Martin, MD
April 29, 2011 -- Women with low vitamin D levels may have an increased risk for the most aggressive breast cancers, new research suggests.
Several earlier studies have suggested a link between low vitamin D levels and breast cancer risk. But the new study is among the first to examine vitamin D insufficiency and poor prognosis.
Researchers from the University of Rochester Medical Center examined vitamin D levels in 155 breast cancer patients in the months before or after they had surgery to treat their disease.
They found suboptimal vitamin D levels to be highly predictive of the presence of biological markers associated with more aggressive tumors.
Triple Negative Tumors
Women in the study with triple-negative tumors, which do not respond to hormone treatments, were almost three times more likely to have suboptimal vitamin D levels as women with other breast cancers.
Triple-negative tumors are difficult to treat and they tend to have a worse prognosis than other breast cancers.
"We consistently saw lower vitamin D levels in breast cancer patients with poor prognostic markers," study researcher Luke Peppone, PhD, tells WebMD.
The study participants had surgery for breast cancer between January 2009 and September 2010. Based on testing conducted within a year before or after surgery, the patients were considered to have either optimal (32 ng/mL or greater) or suboptimal (less than 32 ng/mL) vitamin D levels.
All patients also had a relatively new test designed to predict their risk of recurrence based on the presence of genes that have been identified with breast cancer.
The researchers reported a strong correlation between decreasing vitamin D levels and increasing scores on the predictive test.
African-American women and premenopausal women were more likely to have suboptimal vitamin D levels than older, white women.
The study is published online in the Annals of Surgical Oncology.
While the research does not prove that low vitamin D levels influence outcomes in women who develop breast cancers, Peppone says more study is certainly warranted.
American Cancer Society Deputy Chief Medical Officer Len Lichtenfeld, MD, agrees.
"The vitamin D research as a whole is certainly intriguing, but we have learned many times before that what appears intriguing doesn't always hold up when properly studied," he tells WebMD.
The independent health policy group Institute of Medicine (IOM) recently weighed in on vitamin D and cancer, calling the evidence that vitamin D prevents breast and other cancers "inconsistent and inconclusive."
Vitamin D is produced by the body from the sun's rays. It is found in salmon, tuna, and other oily fish and is added to dairy products. But experts agree that it would be very difficult to get enough vitamin D from food sources alone.
The panel recommended a daily intake of 600 international units (IU) from age 1 to 70 and 800 IU over age 70.
"The [IOM] experts did not dismiss the idea that vitamin D may have a role in preventing cancer or affecting its course once it develops," Lichtenfeld says. "They recognized that the research is trending in this direction, but did not feel that it met the threshold for concluding that a cause-and-effect relationship exists."
Breast cancer specialist Sharon M. Rosenbaum Smith, MD, of St. Luke's-Roosevelt Medical Center in New York, agrees that the new study deserves follow-up.
"We are seeing study after study suggesting a link between vitamin D and breast cancer," she says. "But what that exact link is has yet to be determined."
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