Abstract
1044 Background: The effect of long-term potent BP use on calcium homeostasis in MBC pts is poorly understood. These effects and the need for calcium and Vitamin D supplementation may have significant implications for pt management in both the metastatic and adjuvant settings. Methods: We evaluated serum calcium (sCa), PTH, and 25(OH)D levels and their inter-relationships in 30 MBC pts after prolonged BP use for bone metastases (BM), compared with a control group (CG) of 1484 normal women without bone or mineral disease (JCEM 2003;88:185). The MBC pts were prescribed oral calcium (1g/d) and vitamin D (400IU/d) for 1 month prior to analysis. To determine whether MBC pts differed from CG with respect to the sCa-PTH correlation, logistic regression was performed with sCa, log-transformed PTH and an interaction term (Ca × lnPTH). Results: Mean age of the two groups did not differ [MBC group (58.5 ± 2.0 yr) vs. CG (55.2 ± 0.4 yr, p >.05)]. VitD-deficiency (25vitD < 40 nM) was equally prevalent in the two groups [MBC (23%) vs. CG (25%)]. sCa was significantly higher in MBC pts (2.473 ± 0.019 mM) compared to CG (2.377 ± 0.003, p <0.001). However, PTH was not decreased in MBC pts (4.60 ± 0.36 pM), compared to CG (4.56 ± 0.06, t-test, p=0.91). Logistic regression was highly significant (p<0.0001), as were coefficients for both explanatory variables (sCa, p <0.0001 and lnPTH, p = 0.009) and their interaction (p=0.011). Conclusion: In pts with BM and prolonged BP use there appears to be a shift in the calcium set-point such that PTH release is activated by higher levels of sCa than in controls. We are currently studying whether prophylaxis for relative vit D deficiency in this population can not only correct this shift but also improve pt symptoms No significant financial relationships to disclose.
Published Version
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