Studies presented at the 2007 San Antonio Breast Cancer Symposium indicate that Zometa® (zoledronic acid) effectively prevents bone loss among postmenopausal breast cancer patients treated with an aromatase inhibitor, and among premenopausal breast cancer patients treated with a combination of hormonal therapies.
The majority of breast cancers are hormone receptor-positive. These cancers are stimulated to grow by the circulating female hormones estrogen and/or progesterone. Women with hormone receptor-positive breast cancer are often treated with hormonal therapy.
Historically, tamoxifen was the main agent used as hormonal therapy for breast cancer patients. More recently, aromatase inhibitors have demonstrated improved outcomes compared to tamoxifen among postmenopausal women. Researchers continue to assess side effects associated with aromatase inhibitors in order to reduce or prevent these complications altogether.
Because aromatase inhibitors suppress estrogen levels, they tend to cause bone loss and can increase fracture risk. Use of drugs that reduce bone loss may therefore benefit women who are treated with an aromatase inhibitor.
Zometa is a bisphosphonate drug that is used for the treatment of cancer-related hypercalcemia (high levels of calcium in the blood) and of bone metastases in patients with advanced cancers.
The study enrolled 602 postmenopausal women with Stage I to Stage IIIA, hormone receptor-positive breast cancer. All the women received treatment with the aromatase inhibitor Femara® (letrozole). In addition, half the women received immediate treatment with Zometa and half received delayed treatment with Zometa. In the delayed group, Zometa was given only after the women showed significant signs of bone loss.
- At 36 months of follow-up, women given immediate Zometa had an average increase of close to 4% in lumbar spine bone density. Women in the delayed Zometa group had an average decrease of roughly 3%.
- The risk of fractures did not differ significantly between the study groups. Fractures occurred in 5.7% of women given immediate Zometa and 6.3% of women in the delayed Zometa group.
- There was a trend toward lower recurrence risk among women given immediate Zometa. This result did not meet the criteria for statistical significance, however, suggesting that it could have occurred by chance alone.
- Zometa appeared to be safe and well tolerated.
These results indicate that Zometa effectively prevents bone loss in postmenopausal women with early breast cancer who are receiving adjuvant treatment with an aromatase inhibitor.
In another study, researchers evaluated the effect of Zometa among premenopausal women with early-stage, hormone receptor-positive breast cancer. After surgery, patients received a combination of hormonal therapies. Women were treated with either Zoladex® (goserelin) plus tamoxifen or Zoladex plus the aromatase inhibitor Arimidex® (anastrozole). In addition, half the women received treatment with Zometa.
- After three years women who did not receive Zometa had an average decrease in bone density of 11%. Women who did receive Zometa did not have a significant change in bone density.
- After five years women who did not receive Zometa still showed impairment in bone density, with an average decrease of 6.8% compared to baseline. Women who did receive Zometa had an average increase in bone density of 3.9%.
The researchers conclude that Zometa prevents treatment-related bone loss in premenopausal breast cancer patients receiving a combination of hormonal therapies, and leads to improved bone density at five years.
Brufsky A, Bosserman L, Caradonna R et al. The effect of zoledronic acid on aromatase inhibitor-associated bone loss in postmenopausal women with early breast cancer receiving adjuvant letrozole: the Z-FAST study 36 month follow-up. Presented at the 30th Annual San Antonio Breast Cancer Symposium. San Antonio, TX, December 13-16, 2007. Abstract #27.
 Gnant M, Mlineritsch B, Luschin-Ebengreuth G. Bone mineral density (BMD) at 5 years after diagnosis in premenopausal patients with endocrine-responsive breast cancer, after 3 years of adjuvant endocrine treatment with goserelin and tamoxifen or anastrozole or both treatments in combination with zoledronic acid – new results from ABCSG-12. Presented at the 30th Annual San Antonio Breast Cancer Symposium. San Antonio, TX, December 13-16, 2007. Abstract #26.