Renal Function Changes and NHS Resource Use in Breast Cancer Patients with Metastatic Bone Disease Treated with IV Zoledronic Acid or Oral Ibandronic Acid: a Four-centre Non-interventional Study

Aims: To describe renal function monitoring practice in patients with metastatic bone disease (MBD) treated with IV zoledronic acid (ZA) and oral ibandronic acid (IA), the management pathways and NHS hospital resources used.

Methods: Medical records of 189 patients; IA (91), ZA (98) with primary breast cancer and MBD were reviewed, and data collected on renal monitoring and hospital visits during bisphosphonate therapy. Time and motion review of resources to administer the bisphosphonates was also conducted.

Results: Only 30% of patients given ZA and no patient given IA had baseline creatinine clearance (CrCl) recorded. Calculated baseline CrCl suggested impaired renal function in 33% ZA and 29% IA patients. Dose reductions were not made correctly in 29 ZA and 2 IA patients whose monitoring suggested it. ZA patients made more clinic and day care attendances than IA-treated patients, at twice the cost. Staff activity and patient time per visit was higher with ZA than IA.

Conclusion: Although limited by retrospective design, these results demonstrate that in many patients, CrCl is not calculated before or during treatment with bisphosphonates. Renal function deteriorated in many patients during therapy. In view of these effects, practice should be reviewed to ensure appropriate dosing.