Lack of difference in acute nephrotoxicity of intravenous bisphosphonates zoledronic acid and ibandronate in women with breast cancer and bone metastases.

BACKGROUND

More than 50% of patients with advanced breast cancer develop bone metastases that may lead to multiple complications such as pathological fractures, bone pain or hypercalcaemia. The standard treatment, besides endocrine, targeted-therapy or chemotherapy, is the use of bisphosphonates. However, one of their main adverse side-effects is bisphosphonate-induced nephrotoxicity. The mechanism by which the latter occurs is not well-understood, although emerging evidence suggests that the effect of bisphosphonates on the kidney may differ between agents.

PATIENTS AND

METHODS

The aim of this evaluation was to compare the renal toxicity of 6 mg ibandronate i.v. versus 4 mg zoledronic acid i.v. over a period of six months in women with breast cancer and bone metastases. A prospective randomized trial was carried out to examine specific kidney and other parameters (α1- and β2-microglobulin, albumin, α2-macroglobulin, IgG and C-reactive protein (CRP) generated from spontaneous urine samples from 17 patients of each group.

RESULTS

We were unable to find any significant difference between the two treatment groups with regard to renal toxicity. All patients, independently of the applied bisphosphonate, experienced only temporary renal dysfunction without any evidence of irreversible damage in terms of acute nephrotoxicity during the study period. α1-Microglobulin, a marker for proximal tubular damage, in particular, was not differently elevated in either group.

CONCLUSION

Both applied bisphosphonates were found to be well-tolerated and safe with regard to renal toxicity during a six-month treatment period in patients with otherwise healthy kidneys having advanced breast cancer and bone metastases.