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 pre-menopausal women include:
Because estrogen also helps keep bones strong, lower estrogen levels brought on by hormonal therapy can cause bone loss, which makes bones weak.
The study reviewed here found that when pre-menopausal 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:
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:
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:
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 pre-menopausal women diagnosed with early-stage breast cancer.
If you're a pre-menopausal 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.
VIENNA, Austria, Aug. 20 (MedPage Today) -- In premenopausal patients with early-stage breast cancer taking endocrine therapy, bone mineral density remained stable with a bisphosphonate and improved over time, according to a multicenter randomized trial.
Patients given zoledronic acid (Zometa) during combined endocrine therapy had no significant change in lumbar spine or trochanter bone density at three years, Michael Gnant, M.D., of the University of Vienna, and colleagues reported in the September issue of Lancet Oncology. At five years, bone density at both sites had improved significantly.
In contrast, patients who received endocrine therapy without zoledronic acid lost 11.3% of baseline lumbar spine bone density and 7.3% of trochanter bone density after three years. Bone density increased but did not recover to baseline levels during two additional years of follow-up.
Despite the favorable results with zoledronic acid, the authors cautioned that the long-term bone effects of endocrine therapy remain unclear.
"At five years of follow-up, it is not possible to assess whether these women will ultimately regain their baseline bone mineral density, or whether any bone mineral density improvement will be sufficient to prevent fractures in the future," they said. "Because bone strength, and therefore fracture resistance, is determined by both bone mineral density and bone structural properties, the unknown long-term effects of endocrine therapy on bone microarchitecture might be of great importance."
The findings came from a bone substudy of an 1,800-patient randomized trial to evaluate combined adjuvant endocrine therapy in premenopausal patients with early-stage breast cancer. The patients were randomized to three years of treatment with goserelin plus anastrozole (Arimidex) or tamoxifen. Patients in both groups were further randomized to zoledonic acid or no additional therapy. The 404-patient substudy was designed to assess the long-term effects of endocrine therapy on bone mineral density.
How the patients' bone density might change after cessation of adjuvant therapy is not entirely clear, the authors noted.
Follow-up in the trial continued for an additional two years after therapy ended. Dr. Gnant initially reported the results of the bone substudy late last year. (See: Zoledronic Acid Prevents Bone Loss during Endocrine Therapy)
The five-year results showed that lumbar spine bone density remained 6.3% below baseline (P=0.001) and that trochanter bone density was 4.1% lower (P=0.058) in patients who did not receive zoledronic acid. Patients given the bisphosphonate with endocrine therapy had a 4% increase in lumbar spine bone density and a 3.9% increase in trochanter bone density compared with baseline (P=0.02, P=0.07, respectively).
The findings extend those of another recent study showing that zoledronic acid prevented bone loss in premenopausal women who received adjuvant chemotherapy for early-stage breast cancer. (See: Bisphosphonate Prevents Bone Loss during Breast Cancer Therapy)
The study was sponsored by AstraZeneca and Novartis.
Dr. Gnant disclosed research support, consulting fees, lecture fees, and honoraria from AstraZeneca, Novartis, Roche, Sanofi-Aventis, and Amgen. Coauthor Gunther Steger disclosed honoraria from AstraZeneca and Novartis.
Primary source: Lancet Oncology Source reference: Gnant M et al. "Adjuvant endocrine therapy plus zoledronic acid in premenopausal women with early-stage breast cancer: 5-year follow-up of the ABCSG-12 bone-mineral density substudy" Lancet Oncol 2008; 9: 840-849.
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