P3-5-3 - Changes of N-Telopeptide Crosslinked Type 1 Collagen in Breast Cancer Patients with Bone Metastasis Receiving Denosumab

Abstract

Background: It has been reported that bone metastasis (BM) with breast cancer causes skeletal-related events (SREs) that worsen quality of life and increased risk of mortality. Denosumab and zoledronic acid are effective in delaying or preventing SREs in patients with BM from solid tumor. Retrospective study has reported that normalized urinary N-telopeptide crosslinked type 1 collagen (u-NTx) after 3 months of zoledronic acid correlates with improved SREs-free survival in breast cancer patients with BM. We investigated the changes of u-NTx in breast cancer patients with BM receiving denosumab.Patients and methods: From 2012 to 2013, we enrolled 12 breast cancer patients with BM (multiple metastases: 9 patients, oligo-metastases: 3 patients). 9 patients had denosumab for the first time, and the other 3 patients converted from zoledronic acid to denosumab. Median age was 66 years, range 31-84 years. ER positive was 8 patients, HER2 positive was 1 patient, and triple negative was 3 patients. 7 patients had chemotherapy (CT), 4 patients had endocrine therapy (ET), and 1 patient simultaneously converted from ET to CT with denosumab. We investigated u-NTx at baseline and every 4 weeks after denosumab.Results: Median cycle of denosumab was 7.5 cycles (range 5-15cycles) and median level of u-NTx was 80 nmol bone collagen equivalents (BCE) /mmol creatinine (Cr) (range 11.2-842.5 nmol BCE/mmol Cr). After 2 months of denosumab, u-NTx decreased less than 50 nmol BCE/mmol Cr in all patients without any events of SREs. However, u-NTx of a patient who interrupted denosumab due to osteonecrosis of jaw re-increased over 100 nmol BCE/mmol Cr five months later.Conclusion: This data clarifies the changes of u-NTx in breast cancer patients with BM receiving denosumab. u-NTx measurement may be useful for monitoring the effectiveness of denosumab preventing SREs.