Reducing skeletal complications and bone pain with intravenous ibandronate for metastatic bone disease

Additive growth inhibitory effects of ibandronate and antiestrogens in estrogen receptor-positive breast cancer cell lines

INTRODUCTION

Bisphosphonates are inhibitors of osteoclast-mediated tumor-stimulated osteolysis, and they have become standard therapy for the management of bone metastases from breast cancer. These drugs can also directly induce growth inhibition and apoptosis of osteotropic cancer cells, including estrogen receptor-positive (ER+) breast cancer cells.

METHODS

We examined the anti-proliferative properties of ibandronate on two ER+ breast cancer cell lines (MCF-7 and IBEP-2), and on one ER negative (ER-) cell line (MDA-MB-231). Experiments were performed in steroid-free medium to assess ER regulation and the effect of ibandronate in combination with estrogen or antiestrogens.

RESULTS

Ibandronate inhibited cancer cell growth in a dose- and time-dependent manner (approximate IC50: 10(-4) M for MCF-7 and IBEP-2 cells; 3 x 10(-4) M for MDA-MB-231 cells), partly through apoptosis induction. It completely abolished the mitogenic effect induced by 17beta-estradiol in ER+ breast cancer cells, but affected neither ER regulation nor estrogen-induced progesterone receptor expression, as documented in MCF-7 cells. Moreover, ibandronate enhanced the growth inhibitory action of partial (4-hydroxytamoxifen) and pure (ICI 182,780, now called fluvestrant or Faslodex) antiestrogens in estrogen-sensitive breast cancer cells. Combination analysis identified additive interactions between ibandronate and ER antagonists.

CONCLUSION

These data constitute the first in vitro evidence for additive effects between ibandronate and antiestrogens, supporting their combined use for the treatment of bone metastases from breast cancer.

Efficacy of Ibandronate in Metastatic Bone Disease: Review of Clinical Data

Metastatic bone disease affects many cancer patients and has a significant disease burden because of complications such as pathologic fractures and severe pain, which affect patient mobility and quality of life. Bisphosphonates are the current standard of care for treating metastatic bone disease. Available agents have shown varying degrees of efficacy in clinical trials, and treatment potential can be limited by efficacy, tolerance, or toxicity issues. Ibandronate (Bondronat); F. Hoffman-La Roche Ltd., Basel, Switzerland, http://www.roche.com) is a highly potent, single-nitrogen bisphosphonate that is available in i.v. and oral formulations. In phase III trials in breast cancer patients, both formulations reduced the incidence of skeletal complications associated with metastatic bone disease and had significant and sustained effects on bone pain and patient quality of life. Open-label studies of loading-dose ibandronate administered over consecutive days suggest it also may be useful for relieving severe or opioid-resistant metastatic bone pain. New trials have been designed or are in progress that may extend the clinical indications of ibandronate for patients with metastatic bone disease.

Efficacy and safety of ibandronate in the treatment of neoplastic bone disease

Bone is an organ commonly involved in spreading neoplastic disease, especially in multiple myeloma and carcinoma of the breast, prostate and lung. Skeletal stabilisation and pain relief are the main treatment goals in metastatic bone disease. Bisphosphonate treatment inhibits osseous breakdown and is well-established as the current standard therapy for reducing complications of neoplastic bone disease (e.g., pain, fractures and hypercalcaemia). Ibandronate is a third-generation bisphosphonate that has recently been approved for the treatment of bone metastases caused by breast cancer. The oral and intravenous formulations of ibandronate appear to have comparable efficacy. Ibandronate has also been shown to provide significant and sustained relief from metastatic bone pain over 2 years of treatment, improving patient functioning and quality of life. With a favourable long-term safety profile and the added convenience and flexibility offered by its efficacious oral formulation, ibandronate represents a new therapeutic option for metastatic bone disease management.