CHICAGO – The bone loss associated with aromatase inhibitors was significantly slowed with increasing supplements of vitamin D in a prospective cohort study of 156 postmenopausal women.
"The bone loss was less, the higher your vitamin D level was maintained," said session chair Dr. Thomas J. Smith of Massey Cancer Center of Virginia Commonwealth University. "This is one of the first intervention studies," he said. "And the results are pretty striking."
Dr. Thomas J. Smith
Dr. Sonia Servitja of Hospital del Mar in Barcelona, and colleagues, assessed the association between 25-hydroxy-vitamin D (25(OH)D) concentrations and bone loss at baseline, after 3 months of supplementation, and after 1 year, in patients receiving aromatase inhibitor therapy for early-stage breast cancer.
The 156 women in the prospective cohort had hormone-positive breast cancer and had initiated aromatase inhibitors from January 2006 to June 2009.
All patients received daily oral calcium (1 g) and vitamin D3 (800 IU). Patients with a baseline level of 25(OH)D less than 30 ng/mL received additional oral vitamin D3. The women were a mean age of 62 years with a mean age of menopause onset of 50 years.
The magnitude of the bone-loss prevention correlated with incremental increases in 25(OH)D concentrations.
Each 10-ng/mL increase in 25(OH)D concentration at 3 months appeared to be associated with a 0.55% decrease in bone loss, which was almost a third of the average bone loss experienced by these patients, according to the study findings, presented as a poster at the annual meeting of the American Society of Clinical Oncology.
The findings suggest that vitamin D supplementation at doses higher than the standard of 400 to 800 IU/day might be useful to minimize bone loss in women starting out on aromatase inhibitors and who are not eligible for bisphosphonate therapy according to current guidelines.
Patients who achieved 25(OH)D concentrations greater than or equal to 40 ng/mL at 3 months experienced significantly reduced bone loss. In addition, 25(OH)D increases at 3 months were protective for relative bone loss (adjusted beta for each quintile 1.01%, P value less than .001).
Dr. Servitja disclosed no relevant relationships. Dr. Smith disclosed research funding from the American Cancer Society and the National Cancer Institute.