Metastatic breast cancer is cancer that has spread to parts of the body away from the breast. In up to 80% of women diagnosed with metastatic breast cancer, the cancer spreads to one or more bones. Bone metastases are painful and can weaken bones. Doctors use the term “skeletal-related event” when talking about any of these complications related to cancer that has spread to the bones:
- breaking a bone with metastatic cancer in it
- needing radiation therapy or surgery to ease bone pain or other complications from the cancer
- spinal cord compression caused by the vertebrae (back bones) weakening or collapsing
Zometa (chemical name: zoledronic acid) is used to strengthen bones in women diagnosed with metastatic breast cancer that has spread to the bones. Zometa also is used to lower the risk of a skeletal-related event.
Aredia (chemical name: pamidronate) also is used to reduce bone complications and bone pain caused by metastatic breast cancer that has spread to the bones.
Both Zometa and Aredia are given intravenously, usually every 4 weeks.
A study suggests that after being treated with the regular dose of Zometa and/or Aredia for a year, women with bone metastases can get Zometa every 12 weeks and still get the same benefits from the medicine while reducing their risk of side effects.
The research was published online on Jan. 26, 2017 by JAMA Oncology. Read the abstract of “Continued Treatment Effect of Zoledronic Acid Dosing Every 12 vs 4 Weeks in Women With Breast Cancer Metastatic to Bone: The OPTIMIZE-2 Randomized Clinical Trial.”
Dr. Gabriel Hortobagyi, professor of medical oncology at the University of Texas MD Anderson Cancer Center, is the lead author of the study. Dr. Hortobagyi also is a member of the Breastcancer.org Professional Advisory Board.
Zometa and Aredia are bisphosphonates. Bisphosphonates limit the activity of certain bone cells, called osteoclasts, which help cause bone weakening and breakdown.
Research has shown that bisphosphonates can increase the risk of atypical femur fractures when taken for 5 years or longer. The femur is the large leg bone that runs from your hip to your knee. An atypical fracture means that the bone is broken in an unusual spot. Still, atypical femur fractures are rare -- only about 0.22% of women taking a bisphosphonate for more than 5 years will have an atypical femur fracture.
Bisphosphonates also can sometimes cause another rare but serious side effect, osteonecrosis of the jaw, a condition in which the cells in the jawbone start to die. Researchers think that osteonecrosis of the jaw may develop because bisphosphonates stop the body from repairing microscopic damage to the jawbone that can happen during routine dental procedures or from everyday wear and tear. But it's still not clear why this happens in some people and not in others.
Bisphosphonates also may cause kidney problems, sometimes severe.
Because of the risk of these side effects, doctors wanted to see if women could receive Zometa less often and still get the same benefits.
In this study, called the OPTIMIZE-2 trial, 403 women diagnosed with breast cancer that had spread to the bones were randomly assigned to receive:
- Zometa once every 4 weeks (200 women)
- Zometa once every 12 weeks (203 women)
for 1 year.
The women had already been treated with Zometa and/or Aredia for about a year.
The women who were being treated with Zometa every 12 weeks actually received an infusion every 4 weeks. The first infusion was Zometa and then on weeks 8 and 12 they received a placebo infusion (intravenous fluids that contain no medicine). This was so the women couldn’t tell how often they were being treated with Zometa.
The women were about 59 years old and about 87% of them were white.
The researchers wanted to see if women who were treated with Zometa less often had more skeletal-related events due to breast cancer.
After about a year of follow-up, the researchers found that skeletal-related events were about the same in both treatment groups:
- 22% of the women treated with Zometa every 4 weeks had a skeletal-related event
- 23.2% of the women treated with Zometa every 12 weeks had a skeletal-related event
There also was no difference between the two treatment groups in how long it took for the women to have a skeletal-related event.
This strongly suggests that receiving Zometa every 12 weeks offers the same benefits as receiving it every 4 weeks.
While this report didn’t discuss side effects between the two treatment groups, an earlier analysis that was presented at the 2014 American Society of Clinical Oncology Annual Meeting found that about 25% of the women in both treatment groups had side effects. Still, women who got Zometa every 12 weeks tended to have fewer severe side effects.
If you’ve been diagnosed with metastatic breast cancer that has spread to one or more bones, you and your doctor will develop a treatment plan to minimize any pain you have and reduce your risk of bone complications. If Zometa or another bisphosphonate is part of your treatment plan, you may want to talk to your doctor about this study and ask if it makes sense for you to get Zometa less frequently after the first year. Together, you can develop a treatment plan that’s best for you and your unique situation.
You can learn much more about Zometa and other medicines used to keep bones strong in the Breastcancer.org Bone Health pages.