Ibandronic Acid Continues To Prevent Bone Loss Caused By Anastrozole In Women With Surgically Treated Breast Cancer

Main Category: Bones / Orthopedics
Also Included In: Women's Health / Gynecology;  Breast Cancer
Article Date: 03 Jun 2008 - 1:00 PDT

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Ibandronic acid is an effective treatment option for post-menopausal women with early breast cancer that suffer from low bone mineral density caused by adjuvant anastrozole therapy, according to results from the ARIBON study presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago. [1]

Although anastrozole is a highly effective and well tolerated treatment for breast cancer, its use is associated with a decline in bone mineral density (BMD) and an increased risk of bone fracture in some women.[2,3] The new data show that monthly oral ibandronic acid (also known as ibandronate) treatment significantly increased bone mineral density1 and prevented bone loss caused by anastrozole in patients who were osteopenic (had mild thinning of the bones).

"The results are very reassuring as they show that the strengthening effect of monthly ibandronate at the spine and at the hip is maintained after two years," said Dr Jim Lester, lead study investigator, Cancer Research Centre, Weston Park Hospital, Sheffield, UK. "Anastrozole is an important therapy for breast cancer patients but we clearly want to reduce their risk of declining bone density and resultant fractures and osteoporosis. A bisphosphonate in tablet form, taken once-a-month, offers a promising solution for physicians prescribing anastrozole to breast cancer patients."

The ARIBON study evaluated the impact of ibandronate, 150mg orally once a month, on BMD in post-menopausal early breast cancer patients taking anastrozole. Differences in BMD change at the lumbar spine after one year, between osteopenic patients taking anastrozole plus ibandronate and those in the placebo group was 5.5% (p<0.01). After two years, this difference increased to 6.2% (p<0.01). Differences in BMD change at the hip after one year, between osteopenic patients taking anastrozole plus ibandronate and those in the placebo group was 3.2% (p<0.01). After two years, this difference increased to 4.5% (p<0.01). These results confirm that the addition of ibandronate to anastrozole leads to significant increase in BMD at the spine and the hip after one year and that this positive effect is maintained after two years.

Additionally, changes in the levels of biochemical markers of bone metabolism and related short-term marker changes with subsequent changes in BMD were observed. Differences between ibandronate and placebo treated patients were highly significant for each marker at one year (p<0.001), demonstrating that monthly oral ibandronate normalises bone turnover in patients treated with anastrozole.

Ibandronate is not currently licensed for osteopenia but is licensed for reduction of vertebral fracture risk in osteoporosis. The ARIBON trial is the first study to report two-year data on the use of an oral bisphosphonate for the treatment of anastrozole induced bone loss.

About ARIBON

The ARIBON trial is a double blind, randomised, placebo-controlled study designed to evaluate the impact of bisphosphonate treatment on bone mineral density (BMD) in 131 post-menopausal women taking anastrozole for early breast cancer.

The primary endpoint was the change in BMD at the lumbar spine and hip at one and two years for the anastrozole plus ibandronate treated patients compared with those receiving anastrozole plus placebo.

Secondary endpoints included the changes in bone resorption and formation markers over time and adverse events including any fractures with and without bisphosphonates.

About ibandronic acid

In the UK, ibandronic acid is currently licensed for the treatment of tumour-induced hypercalcaemia of malignancy (with or without metastases) and for the prevention of skeletal events in patients with breast cancer and bone metastases - MBD. It has been shown to be an effective treatment for preventing bone fractures and relieving bone pain in metastatic breast cancer in three randomised trials. Additionally a superior renal safety profile, demonstrated in randomised trials, means that it limits the risk of kidney deterioration or failure that has been associated with other i.v. bisphosphonates. Intravenous Bondronat (ibandronic acid) has a renal safety profile which gave no increased risk of renal adverse events compared with placebo for up to four years of treatment.

In addition, ibandronic acid is licensed for the treatment of osteoporosis in post menopausal women at increased risk of fracture. It leads to progressive net gain in bone mass and a decreased incidence of fractures through the reduction of elevated bone turnover.

The most common side effects following intravenous administration are injection-site reaction and flu-like syndrome. For oral administration, the most common side effects are gastrointestinal discomfort and dyspepsia.

About anastrozole

Anastrozole is an effective aromatase inhibitor which prolongs relapse-free survival in women with hormone receptor positive early breast cancer, and has superior efficacy and tolerability over tamoxifen. [4] Anastrozole use, however, is associated with a decline in bone mineral density and increased risk of bone fracture in some women. [2,3] Treatment for 5 years with anastrozole is associated with a bone loss of 6% to 7% at the lumbar spine and hip respectively. [3]

About Roche in the UK

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References

1. Lester JE, Gutcher SA, Ellis S, et al. Use of monthly oral ibandronate to prevent anastrozole- induced bone loss during adjuvant treatment for breast cancer: Two-year results from the ARIBON study. Poster presented at the American Society of Clinical Oncology (ASCO) annual meeting, 1-5 June 2008.

2. Chien A, Goss P. Aromatase inhibitors and bone health in women with breast cancer. Journal of Clinical Oncology. 2006. 24;5305-5312.

3. R. E. Coleman ATAC Trialists' Group. Effect of anastrozole on bone mineral density: 5-year results from the 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial. Journal of Clinical Oncology, 2006 ASCO Annual Meeting Proceedings (Post-Meeting Edition). Vol 24, No 18S (June 20 Supplement), 2006: 511.

4. Howell A, Cuzick J, Baum M, et al. Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer. Lancet. 2005;365(9453):60-2.

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