Breast cancer, osteoporosis and vitamin D

Aromatase inhibitors (AIs) are used in the treatment of estrogen–dependent breast and ovarian cancer in postmenopausal women, since the enzyme aromatase synthesizes estrogen. However, their use implies risk of osteoporosis and bone loss, and is associated with increased fracture rates. It is thought that vitamin D might play a role in minimising this effect.

To test this, Xavier Nogués and colleagues from the Genetic Study of Osteoporosis research group at the IMIM-Hospital del Mar have recently undergone a study in which they followed up a cohort of 232 women under AI treatment for early breast cancer. These women were ineligible for bisphosphonate therapy (usually used to reduce the risk of osteoporosis) and stayed on treatment for 1 year. They were supplemented with daily calcium (1 g) and vitamin D, as well as additional oral vitamin D every 2 weeks if their baseline vitamin D concentration was lower than 30 ng/ml.

Serum vitamin D was measured at baseline and 3 months, and lumbar spine (LS) bone mineral density at baseline and 1 year. The results, published in the journal Breast Cancer Research Treatment show that after a year on AI therapy, the participants experienced a significant 1.68 % bone loss at the lumbar spine (LS). High vitamin D at 3 months protected against LS bone loss, and those who reached the highest levels (≥40 ng/ml) had reduced bone loss by 1.70 % compared to those with low vitamin D levels (<30 ng/ml).

Nogués and colleagues conclude that improved vitamin D status using supplementation can indeed decrease the AI-associated bone loss. And they warn that, according to their results, the current Institute of Medicine target recommendation of 20 ng/ml might be too low to ensure good bone health.

Reference:
Prieto-Alhambra D, Servitja S, Javaid MK, Garrigós L, Arden NK, Cooper C, Albanell J, Tusquets I, Diez-Perez A, Nogues X. Vitamin D threshold to prevent aromatase inhibitor-related bone loss: the B-ABLE prospective cohort study. Breast Cancer Res Treat. 2012 Mar 21;

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