In premenopausal women, chemotherapy to treat early-stage breast cancer can cause the ovaries to shut down, either temporarily or permanently. Because the ovaries produce most of the estrogen in a premenopausal woman's body, shutting down the ovaries causes a big drop in estrogen levels. Estrogen helps keep bones strong, so a drop in estrogen levels during and after chemotherapy can cause bone loss, which makes bones weak.
A small study found that giving Zometa (chemical name: zoledronic acid) during and after chemotherapy for early-stage breast cancer kept bone density stable in premenopausal women. The women who didn't get Zometa during and after chemotherapy had some bone loss.
Spine and hip bone strength was determined by measuring bone mineral density. Bone mineral density is lower in weaker bones and higher in stronger bones. The researchers measured bone mineral density three times in the study:
- at the start of chemotherapy
- 6 months after chemotherapy
- 12 months after chemotherapy
The women who got Zometa didn't lose a significant amount of bone in the year after chemotherapy; their bone mineral density measurement was the same each time it was measured.
The women who got a placebo instead of Zometa had some loss of bone in the year after chemotherapy:
- 6 months after chemotherapy, spine bone mineral density dropped 2.2% and hip bone mineral density dropped 0.8%
- 12 months after chemotherapy, spine bone mineral density dropped 4.1% and hip bone mineral density dropped 2.6%
Blood tests also showed that the women who didn't get Zometa were experiencing bone loss.
Another part of this research showed that Zometa can prevent bone loss in premenopausal women who get hormonal therapy medicine to treat breast cancer.
This study does have some weaknesses. The women received Zometa intravenously every 3 months, but it's not clear if that schedule is the best. It was also difficult to get women to participate in the study and to keep those who did decide to participate. This might be why the study was small (101 women).
Zometa belongs to a group of medicines called bisphosphonates. Bisphosphonates help prevent bone loss and can build bone strength. Other bisphosphonates are:
- Fosamax (chemical name: alendronate)
- Actonel (chemical name: risedronate)
- Aredia (chemical name: pamidronate)
- Bonefos (chemical name: clodronate)
- Boniva (chemical name: ibandronate)
- Reclast (chemical name: zoledronic acid, but a different formulation than Zometa)
Some bisphosphonates, such as Fosamax and Actonel, are pills taken by mouth. Zometa, Aredia, and Bonefos are given intravenously. Besides Zometa, research has shown that Aredia, Bonefos, and Fosamax have some ability to protect bones during and after chemotherapy for breast cancer.
If you're a premenopausal woman and chemotherapy is part of your treatment plan for early-stage breast cancer, ask your doctor how chemotherapy might affect your bones and the steps you can take to minimize any effects.
Visit the Breastcancer.org Bone Health section to learn more about measuring bone health, how breast cancer treatment can affect your bones, and ways you can keep your bones healthy and strong during and after treatment.