To lower the risk of hormone-receptor-positive breast cancer coming back (recurrence), hormonal therapy (also called endocrine therapy) is often part of the treatment plan. Hormonal therapy lowers the amount of estrogen in the body. Hormonal therapy options for premenopausal women include:
- medicines that temporarily or permanently shut down the ovaries (medical ovarian shutdown)
- surgically removing the ovaries (oophorectomy)
Because estrogen also helps keep bones strong, lower estrogen levels brought on by hormonal therapy can cause bone loss, which makes bones weak.
A study found that when premenopausal women diagnosed with hormone-receptor-positive, early-stage breast cancer got Zometa (chemical name: zoledronic acid) along with hormonal therapy, their bone density stayed the same before and after treatment. Women who didn't get Zometa along with their hormonal therapy had significant bone loss in the years after treatment.
The 404 women in the study were treated for 3 years with goserelin (brand name: Zoladex), a medicine that stops the ovaries from making estrogen (ovarian shutdown) and either tamoxifen or Arimidex (chemical name: anastrozole). About half of the women also got Zometa, given intravenously twice a year for 3 years. The other half didn't get Zometa with the hormonal therapy treatment.
The researchers determined spine and hip bone (trochanter bone) strength 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:
- before hormonal therapy started
- 3 years after the start of hormonal therapy
- 5 years after the start of hormonal therapy (2 years after hormonal therapy ended)
The women who got Zometa had the same bone mineral density before and 3 years after hormonal therapy. Five years after hormonal therapy, the women who got Zometa actually had bone mineral density that was about 4% higher than it was before hormonal therapy.
The women who didn't get Zometa had lower bone mineral density 3 years after hormonal therapy started, which means they lost bone. While their bone mineral density was higher at 5 years after hormonal therapy then it was at 3 years after hormonal therapy, bone mineral density at 5 years after hormonal therapy was still lower than it was before hormonal therapy:
- 3 years after hormonal therapy, spine bone mineral density dropped 11.3% and hip bone mineral density dropped 7.3%
- 5 years after hormonal therapy, spine bone mineral density was 6.3% lower and hip bone mineral density was 4.1% lower compared to measurements before hormonal therapy started
Still, it's not clear whether the benefits of Zometa will last longer than 5 years. It's also not clear how the hormonal therapy treatments in this study might affect bone health beyond 5 years after treatment.
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 or hormonal therapy treatment in premenopausal women diagnosed with early-stage breast cancer.
If you're a premenopausal woman diagnosed with hormone-receptor-positive, early-stage breast cancer and chemotherapy, hormonal therapy, or both are part of your treatment plan, ask your doctor how these treatments 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.