Bisphosphonates are medicines used to prevent or treat osteoporosis. Some research has suggested that bisphosphonates also might help stop breast cancer from spreading to the bones by making it harder for breast cancer cells to grow in bones and might help reduce the risk of the cancer coming back (recurrence) in women diagnosed with early-stage breast cancer.
Adding the intravenous bisphosphonate Zometa (chemical name: zoledronic acid) at the start of early-stage breast cancer treatment has been shown to reduce recurrence risk in postmenopausal and older premenopausal women.
But two other studies discussed here found that two oral (taken by mouth) bisphosphonates didn't reduce recurrence risk for women diagnosed with early-stage breast cancer.
The results were presented at the 2011 San Antonio Breast Cancer Symposium.
Bisphosphonates used to prevent or treat osteoporosis include:
- Actonel (chemical name: risedronate)
- Bonefos (chemical name: clodronate)
- Boniva (chemical name: ibandronate)
- Fosamax (chemical name: alendronate)
- Reclast (chemical name: zoledronic acid -- the same active ingredient as Zometa)
Reclast is given intravenously once a year. Boniva can be given intravenously, but usually is taken as a pill by mouth. The others are pills taken by mouth.
Zometa, the intravenous form of zoledronic acid, is used to strengthen bones and lower the risk of breaking a bone and other bone problems in women diagnosed with metastatic breast cancer that has spread to the bones.
The National Surgical Adjuvant Breast and Bowel Project B34 trial (NSABP-B34) involved nearly 3,300 women diagnosed with early-stage breast cancer. Most of the women were older than 50. Right after surgery, the women were treated with chemotherapy and/or hormonal therapy to reduce the risk of recurrence. Half the women also got Bonefos for 3 years. The other women got a placebo (sugar pill). Half the women were followed for more than 8.5 years. The other half were followed for shorter periods of time.
Results from NSABP-B34 show that the time women lived without the cancer coming back (disease-free survival) was the same among women who got Bonefos and women who got the placebo. This means that there was no difference in the risk of breast cancer recurrence.
A finer analysis of the results did find that postmenopausal women older than 60 who got Bonefos were less likely to have metastatic recurrence (the cancer coming back in a part of the body away from the breast).
The German Adjuvant Intergroup Node Positive (GAIN) study involved nearly 3,000 women diagnosed with early-stage breast cancer. After surgery, the women got chemotherapy and hormonal therapy to reduce the risk of recurrence. About 66% of the women also got oral Boniva for 2 years. The other 33% got a placebo. Half the women were followed for more than 3 years and the others were followed for shorter periods of time.
Like the NSABP-B34 results, the GAIN study results found that disease-free survival was the same in women who got oral Boniva and women who got placebo. In the GAIN study, Boniva didn't lower the risk of recurrence, even among older postmenopausal women.
It's important to know that the two bisphosphonates studied, Bonefos and Boniva, are oral bisphosphonates.
Although the studies don't suggest that oral bisphosphonates reduce breast cancer recurrence risk, one of these medicines may still make sense for postmenopausal women to strengthen bones that may be weakened by some breast cancer treatments.
While the intravenous bisphosphonate Zometa isn't routinely prescribed to reduce recurrence risk in women diagnosed with early-stage, hormone-receptor-positive breast cancer right now (and it isn't approved by the U.S. Food and Drug Administration for this use), the results of several studies suggest that using Zometa after surgery could help reduce recurrence risk in some postmenopausal women (and help protect bone health at the same time). So it's possible doctors will start using Zometa in this way.
If you've been diagnosed with early-stage breast cancer, you may want to ask your doctor if a bisphosphonate makes sense for you. If you're a postmenopausal woman, your doctor may recommend a bisphosphonate to strengthen your bones or treat osteoporosis. Research suggests that choosing the intravenous bisphosphonate Zometa could also lower your risk of breast cancer recurrence when started right after surgery. If you're prescribed a bisphosphonate, know that some of them need to be taken in a specific way and all may cause serious side effects; make sure you and your doctor talk about how to take the medicine.
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