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The influence of bisphosphonates on bone turnover markers in patients (pts) with breast cancer (BC).

1058 Background: The relevance of the bone metabolism for the prognosis of BC pts is becoming widely accepted. Bisphosphonates are increasingly used in BC pts as prophylactic (antitumor benefits) or as therapeutic agents for the prevention of skeletal related events (SREs). The bone resorption marker peptide-bound collagen type I cross-links C-telopeptides (ICTP) and the bone formation marker N-terminal propeptide of type I collagen (PINP) may become important tools to monitor the bone metabolism and may be influenced by co-medication.


METHODS
ICTP and PINP were measured in serum samples (n = 252) under standardized conditions. We included BC pts without (n=118, 58±11 yrs) and with bone metastases (BM, n=23, 64 + 12 yrs). For comparison 111 prostate cancer (PC) pts without (n = 84, 70 ± 6 yrs) and with BM (n = 27, 67 ± 10 yrs) were investigated.


RESULTS
The median ICTP (5.41 vs 4.34 ug/l, p = 0.04 [Mann-Whitney test]) and PINP (44.9 vs 36.3 ug/l, p = 0.08) values were higher in BC pts with BM as compared to no BM. The presence of BM (< 3 vs 1-3 mets) increased ICTP and PINP values further, whereas bisphosphonates lead to a significant reduction in PINP to normal values in these pts (58.3 vs 32.8 ug/l, p = 0.01). Tamoxifen increased ICTP (4.85 ± 1.8 ug/l) and decreased PINP (36.7 ± 14.3 ug/l), whereas aromatase inhibitors (AIs) increased ICTP (4.93 ± 1.7 ug/l) and PINP (49.4 ± 24.7 ug/l). The same effects were seen in PC pts with and without BM, LHRH had a similar effect like AIs, whereas the impact of antiandrogens was like tamoxifen. Age and gender had no significant influence on ICTP or PINP in BC and PC pts.


CONCLUSIONS
Markers of bone metabolism may be useful for the diagnosis and follow-up of pts with BC and PC with and without BM. Bone metastases and aromatase inhibitors increased serum ICTP and PINP, whereas bisphosphonates induced a significant decrease in serum PINP. [Table: see text].