Background:
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.
Aim:
We aimed to evaluate the experience of antiresorptive therapy at our health network.
Methods:
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.
Results:
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%)
Conclusions:
Our audit showed a side effect profile similar to registration trials. Extended follow-up is required for those who remain on prolonged treatment.