Low vitamin D plus exemestane tied to bone loss: the connection between vitamin D insufficiency and breast cancer has not been fully examined.(Gynecology)

ATLANTA -- Vitamin D supplementation should be considered for postmenopausal breast cancer patients treated with aromatase inhibitors, Dr. Per E. Lonning reported at the annual meeting of the American Society of Clinic+al Oncology.

"Low vitamin D status could be one of the factors predisposing patients to breast cancer," said Dr. Lonning, a professor at Haukeland University in Bergen, Norway.

Postmenopausal breast cancer patients who were treated with exemestane and had vitamin D deficiency lost bone mineral density (BMD) at a higher rate than all other patients in a Norwegian trial, according to Dr. Lonning, who presented the trial's results

The double-blind study enrolled early breast cancer patients at six sites between January 1999 and October 2001. Participants were postmenopausal with estrogen receptor-negative or progesterone receptor-positive breast cancer. Median patient age was 59.5 years, and all had a low risk of breast cancer recurrence after surgery.

Of the patients enrolled in the randomized, controlled trial, 128 of 147 (87%) had low levels of vitamin D, defined as 30 ng/mL or less.

Investigators randomized 73 women to 25 mg of oral exemestane daily and 74 women to a daily placebo for 2 years. Local guidelines did not routinely offer adjuvant endocrine therapy at the time of the study, the investigators noted. Mean vitamin D levels were reported as 21.6 ng/mL for the exemestane arm and 22.6 ng/mL for the control group.

Average patient change in femoral neck BMD was -4.7% after 2 years of treatment with exemestane, an aromatase inhibitor. Placebo patients with low vitamin D also had bone loss in the femoral neck, but the reduction was -3.0%.