Combining Doxycycline With Bone-Targeted Therapy in Patients With Metastatic Breast Cancer

Potential candidates for this trial must have received intravenous bisphosphonate therapy (i.e. pamidronate or zoledronic acid) or subcutaneous denosumab for at least 3 months. Baseline patient characteristics will be recorded and screening serum PTH (to rule out primary hyperparathyroidism) and vitamin D (25OH-vit D) will be recorded. In order to fulfill the study objectives, serum will be taken for CTX (fasting morning blood sample), P1NP and BSAP as well as for the optional translational studies (e.g. MMP and TIMP levels). Optional urine will be taken for NTX. Questionnaires will also be completed for symptoms (Brief pain inventory (BPI) \[26\] and FACT-BP \[27\]) and analgesic use (converted into an oral Morphine-equivalent dose). The serum, urine and questionnaire data will be collected at: baseline, weeks 4, 8, and 12. In addition, toxicity information and questions about the occurrence of skeletal related events will be performed at baseline, weeks 4, 8 and 12. At baseline and week 12 the patient will also have a bone marrow aspirate and trephine biopsy performed from the posterior iliac crest. These specimens will be used for ER, PR and Her2 analysis (by FISH) and markers of apoptosis (TUNEL) and proliferation (Ki67) and also for optional translational studies providing tumour cells are present.