Persistence with bisphosphonates in patients with metastatic breast cancer: a retrospective database analysis

In women with breast cancer and bone metastasis, compliance to antiresorptive treatment is of upmost importance to ensure maximum effectiveness in clinical practice. The aim of our study was to investigate persistence with oral and intravenous bisphosphonates (BIS) in a large group of women with metastatic breast cancer and to identify the determinants of non-persistence. We used data from the Disease Analyzer database (IMS Health, Germany), which includes 2,067 general practices and 397 gynaecological practices. From a dataset of 20 million patients, we identified 1,045 patients diagnosed between January 2001 and December 2010 with bone metastasis (ICD 10: C795) following breast cancer (ICD 10: C50) with first-time cancer-related bisphosphonate prescriptions (ATC: M03B4). Of these, 763 patients received intravenous treatment, and 280 patients received oral BIS treatment. After 1 year, 35.3 % of patients treated with intravenous, and 45.6 % of patients treated with oral bisphosphonates discontinued their therapy (p = 0.002). Multivariate Cox Regression analyses showed a significant increased risk of treatment discontinuation in patients using intravenous BIS (HR: 0.82) compared with oral BIS. Patients younger than 50 (HR: 1.52) were most likely to discontinue treatment compared with the reference group of women over 70. The use of other treatments, such as chemotherapy or hormone therapy, was associated with a decreased risk of treatment discontinuation. Moreover, treatment discontinuation was higher in West Germany compared with East Germany (HR: 1.65) and in patients covered under private health insurance (HR: 1.33). Persistence with all bisphosphonate treatments in women with breast cancer and bone metastasis is low and needs to be significantly increased to improved outcomes in clinical practice. Further research is required to understand this complex issue.