Researchers from The University of Texas MD Anderson Cancer Center have found that women suffering from metastatic breast cancer of the bone can receive bisphosphonates less often after the first year of administration, this way reducing the risk of serious side effects.
Distant metastases are the cause of about 90% of deaths due to breast cancer, and metastatic breast cancer patients are likely to develop bone metastasis throughout their disease, since bone is one of the primary metastatic sites in this type of cancer.
Bisphosphonates are a class of drugs that prevent the loss of bone mass and are commonly used to treat bone metastasis in different types of cancer. For example, Zoledronate is a high-potency intravenous bisphosphonate that has been shown modify progression of skeletal metastasis in patients suffering from breast cancer.
MD Anderson’s Gabriel Hortobagyi, MD, professor, Breast Medical Oncology, presented clinical data from the OPTIMIZE-2 study on the American Society of Clinical Oncology 2014 Annual Meeting.
This Phase III prospective, randomized, double blind clinical trial enrolled 403 metastatic breast cancer patients who had previously received 9 or more doses of bisphosphonates in their first 10-15 months of therapy. Patients received an additional year of 4 mg IV of zoledronic acid, either every month or every three months for an additional year.
The data from this study showed that skeletal related events (SRE) were comparable in both groups studies (22 vs 23%), with a similar overall safety profile, showing that receiving zoledronic acid every 12 weeks after one year of monthly administration was as efficient as receiving it monthly.
Furthermore, monthly treatment was associated with more kidney-related adverse events (9.6%) when compared to the 12-week group (7.9%).
“With those findings, it became standard of care to continue bisphosphonates for the life of the metastatic breast cancer patient. Yet there were no definitive studies or guidelines confirming this clinical practice or looking at long-term side effects. The OPTIMIZE-2 trial is the largest study designed to date looking at the frequency of bisphosphonate delivery,” said Dr. Hortobagyi, in an MD Anderson press release.
Although promising, the study had some limitations, since it followed patients for one year after the initial bisphosphonates treatment while many patients receive bisphosphonates throughout their entire treatment for metastatic disease, even if they develop an SRE.
However, the results from this clinical study are prone to impact the setting of metastatic breast cancer as well as other solid tumors that rely on monthly intravenous bisphosphonates to prevent SRE’s and bone mass loss.
“In general in breast cancer, we’re getting to the point where our patients are doing well enough that we can begin to start reducing the treatments they receive, as we’re likely over-treating the majority of our patients — and this study is an example of that,” Dr. Hortobagyi added in the press release.