Bone remodeling markers in breast and prostate cancer patients undergoing endocrine and bisphosponate therapy

Abstract

9602 Background: Bone metastases are frequent and often the first manifestation of disseminated tumor spread in patients with breast and prostate cancer. In this regard the bone resorption marker peptide-bound collagen type I cross-links C-telopeptides (ICTP) and bone formation marker N-terminal propeptide of type I collagen (NTX) might be of diagnostic relevance. The serum levels correlate with the presence of bone metastases, however little is known about the influence of endocrine and bisphosphonate therapy. Methods: We prospectively investigated 208 patients (63.4 ± 10.8 yrs) with either breast (n = 95) or prostate cancer (n = 77) without (n = 172) and with (n = 18 breast, n = 18 prostate) bone metastases in this longitudinal follow-up study. ICTP and NTX were measured in serum samples. Patients were treated according to clinical guidelines using endocrine therapy, bisphosphonates and/or radiotherapy if required. Results: At baseline, serum bone marker levels were higher in patients with bone metastases compared to patients without bone metastases (ICTP: 5.44 ± 0.38 vs 4.72 ± 0.17 ug/l, p = .029, NTX 48.3 ± 5.7 vs 41.9 ± 2.2 ug/l p = ns). Bisphosphonate therapy reduced ICTP and NTX values on average by about 0.6 - 0.7 ug/l and 10 - 20 ug/l respectively. Endocrine therapy with Tamoxifen (TAM) reduced ICTP and NTX values whereas aromatase inhibitors (AIs) lead to a reduction of ICTP and an increase of NTX. The serum levels of NTX were significantly higher in patients on AIs as compared to TAM (55.5 ± 9.2 ug/l vs 32.1 ± 2.7 ug/l, p = .016). Conclusions: Bone remodeling markes may be useful for the diagnosis and follow-up of patients with breast and prostate cancer with bone metastases, as well as patients at high risk of developing skeletal metastases. Early detection of bone metastases would otherwise require the repeated use of expensive imaging studies. Sensitive and specific serological markers of bone turnover would be of high clinical value during follow-up of these patients. However, the present data show that the typical comedications given to patients with breast and prostate cancer influence the serum levels of bone remodeling markers. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Novartis Novartis