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.
Zometa is given intravenously, usually every 4 weeks. A study suggests that after 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 presented at the 2014 American Society of Clinical Oncology Annual Meeting on May 31, 2014. Read the abstract of “Efficacy and safety of continued zoledronic acid every 4 weeks versus every 12 weeks in women with bone metastases from breast cancer: Results of the OPTIMIZE-2 trial.”
Dr. Gabriel Hortobagyi, professor of medical oncology at the University of Texas MD Anderson Cancer Center, presented the study. Dr. Hortobagyi also is a member of the Breastcancer.org Professional Advisory Board.
Zometa is a bisphosphonate. 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, as well as reduce the risk of side effects.
In this study, called the OPTIMIZE-2 trial, 412 women diagnosed with breast cancer that had spread to the bones were randomly assigned to receive Zometa either:
- once every 4 weeks
- once every 12 weeks
for 1 year. The women had already been treated with Zometa for about a year.
At the end of the study, the researchers found that skeletal-related events were about the same in both treatment groups:
- 22% of the women who got Zometa every 4 weeks had a skeletal-related event
- 23.2% of the women who got Zometa every 12 weeks had a skeletal-related event
This strongly suggests that receiving Zometa less often offers the same benefits as receiving it more frequently.
While about 25% of the women in both groups had side effects, women who got Zometa every 12 weeks tended to have fewer severe side effects:
- serious kidney problems happened in 7.9% of the women who got Zometa every 12 weeks and in 9.6% of the women who got Zometa every 4 weeks
- two women getting Zometa every 4 weeks developed osteonecrosis of the jaw; none of the women getting Zometa every 12 weeks had this side effect
“The OPTIMIZE-2 trial is the largest study designed to date looking at the frequency of bisphosphonate delivery,” Dr. Hortobagyi explained. “The study determined that giving the therapy less often after a year of earlier treatment was non-inferior than receiving the therapy monthly, and we found that less frequency is likely associated with a reduced toxicity.”
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.