Zometa (chemical name: zoledronic acid) is used to strengthen bones and lower the risk of fractures or other bone complications in women diagnosed with metastatic breast cancer that has spread to the bones. Earlier studies suggested that Zometa also might help stop breast cancer from spreading to the bones by making it harder for breast cancer cells to grow in bones.
Two studies wanted to see if Zometa could reduce the risk of the cancer coming back in women diagnosed with early-stage breast cancer.
One study, called the Austrian Breast Cancer Study Group (ABCSG) XII trial, suggested that treatment with Zometa and hormonal therapy after surgery could reduce the risk of recurrence in premenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer.
The other study, called the Adjuvant Zoledronic Acid to Reduce Recurrence (AZURE) trial, found that treatment with Zometa after surgery didn't really reduce the risk of recurrence of in premenopausal women diagnosed with early-stage breast cancer. Still, the AZURE study did suggest that Zometa might reduce the risk of recurrence in postmenopausal women.
Because of these conflicting results, doctors don't agree on whether Zometa treatment makes sense for some women to reduce the risk of recurrence of early-stage breast cancer.
In the ABCSG trial, 1,808 premenopausal women diagnosed with stage I or II hormone-receptor-positive breast cancer had surgery and then hormonal therapy to reduce recurrence risk. Half the women got Zometa with hormonal therapy and half got only hormonal therapy.
About 4 years after surgery, the women who got Zometa and hormonal therapy had a 36% improvement in disease-free survival compared to the women who got only hormonal therapy. Doctors call the time a woman lives without the cancer coming back disease-free survival. After another year of follow-up, disease-free survival was 32% better in the women who got Zometa and hormonal therapy.
Overall survival in the ABCSG trial -- the time a woman lived whether or not the cancer came back -- was 33% better in women who got Zometa and hormonal therapy. But this difference wasn't statistically significant, which means that it could have been due to chance and not because of the difference in treatments.
In the AZURE trial, 3,360 women diagnosed with stage II or III breast cancer had surgery and then hormonal therapy and/or chemotherapy to reduce the risk of recurrence. Half of the women also got Zometa and the other half did not.
About 5 years after surgery, the women who got Zometa and the women who didn't get Zometa had the same risk of recurrence overall. So Zometa didn't seem to affect disease-free survival in the AZURE trial.
Still, when the researchers looked at premenopausal and postmenopausal women as separate groups, there were different results. Postmenopausal women who got Zometa had a 29% improvement in disease-free survival compared to postmenopausal women who didn't get Zometa. But this difference wasn't statistically significant, which means that it could have been due to chance and not because of the difference in treatments. There was no difference in disease-free survival in premenopausal women, whether or not they got Zometa.
There were some important differences in these two studies, which may be why there are different results:
- The women in the ABSCG trial were all premenopausal. The women in the AZURE trial were both pre- and postmenopausal.
- The ABSCG trial studied only hormone-receptor-positive, stage I or II cancers. The AZURE trial included both hormone-receptor-positive and hormone-receptor-negative cancers that were stage II or III.
Because doctors aren't sure if Zometa can improve disease-free survival in women diagnosed with early-stage breast cancer, it's not routinely used for that purpose at this time.
Still, using Zometa and other bisphosphonates may make sense for postmenopausal women to strengthen bones that may be weakened by some breast cancer treatments.
Bisphosphonates used to prevent or treat osteoporosis include:
- Actonel (chemical name: risedronate)
- 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. The others are pills taken by mouth.
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. Whether Zometa also can lower your risk of recurrence is unclear. 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.