Antiresorptive therapy is a critical component of treatment in the management of patients with metastatic breast cancer with bony metastases. Correlation of community experience with registration trial data is limited.
We aimed to evaluate the experience of antiresorptive therapy at our health network.
Pharmacy records were used to identify patients receiving antiresorptive therapy for metastatic breast cancer over a 5-year period (2010-2014). Evaluation included prescribing habits, incidence of skeletal related events (SRE), choice of agent, dosing intervals, and side effects.
102 patients with evaluable data were identified, median age at diagnosis was 60 years (range 29-90). Median disease duration at censor date was 26 months with a median duration of antiresorptive therapy of 16 months (range 1-108). 23.5% had received at least 3 years of antiresorptive therapy. Most patients started therapy at the time of diagnosis of bone metastases (78.4%). Denosumab was the most common initial agent prescribed (46%) followed by intravenous bisphosphonates (42%). 17.8% of patients changed to an alternative agent, most commonly Denosumab (12/18 patients).
SRE were commonly encountered in this cohort. Including SRE at diagnosis prior to antiresorptive therapy, 51% of patients required radiotherapy to bone, 30.4% had hypercalcaemia, 14.7% required bone surgery, with 6.8% having pathologic fractures and 7.8% cord compression.
21.6% had formal dental review prior to treatment. Vitamin D and Calcium prescription was documented in 39.2% and 34.3%. Renal impairment at diagnosis was seen in 30.4% (22.5% CKD2, 7.8% CKD3).
Hypocalcaemia of any grade occurred in 20.6%, but Grade 3-4 toxicity was rare (2%). Osteonecrosis of the jaw was identified in one patient (1%). Atypical fracture also occurred in one patient (1%)
Our audit showed a side effect profile similar to registration trials. Extended follow-up is required for those who remain on prolonged treatment.