The American Society of Clinical Oncology (ASCO), the world?s leading professional organization representing physicians who care for people with cancer, today issued an update to its clinical practice guideline on the use of bone-modifying agents, in particular, osteoclast inhibitors, to prevent and treat skeletal complications from bone metastases in patients with metastatic breast cancer.
The new guideline includes recommendations on the use of a new drug option, denosumab (Xgeva), and addresses osteonecrosis of the jaw, an uncommon condition that may occur in association with bone-modifying agents. The updated guideline also provides new recommendations on monitoring of patients who undergo treatment with bone-modifying agents and highlights priorities for future research on these drugs.
ASCO?s Bisphosphonates in Breast Cancer Panel conducted a systematic review of the medical literature to develop the new recommendations. The updated guideline, American Society of Clinical Oncology Clinical Practice Guideline Update on the Role of Bone-Modifying Agents in Metastatic Breast Cancer, was published online today in the Journal of Clinical Oncology.
Not one over the other
The guideline recommends that patients with breast cancer who have evidence of bone metastases be given one of three agents ? denosumab, pamidronate or zoledronic acid ? approved by the U.S. Food and Drug Administration (FDA). It does not support use of any one drug over the others. These drugs are all considered osteoclast inhibitors, but they belong to different drug families: pamidronate and zoledronic acid are part of a class of drugs called bisphosphonates, while denosumab is a monoclonal antibody that targets receptor activator of nuclear factor-kappa beta ligand (RANKL).
Not sufficient evidence
The guideline also recommends against initiating bone-modifying agents in the absence of bone metastases outside of a clinical trial. It notes that an abnormal bone scan result alone, without confirmation by a radiograph, CT or MRI scan, is not sufficient evidence to support treatment with these drugs.
Selecting individual therapy
?The updated recommendations take into account recent progress in controlling potential bone damage in metastatic breast cancer,? said Catherine Van Poznak, MD, co-chair of the Bisphosphonates in Breast Cancer Panel and assistant professor of medicine at the University of Michigan. ?We?ve established that a growing number of osteoclast inhibitors can have a positive effect and decrease of the risk of skeletal-related events in women with bone metastases. Because many factors ? including medical and economic ? must be considered when selecting a therapy for an individual, it?s good to have several effective choices.?
Bone is one of the most common sites to which breast cancer spreads. Bone metastases occur in approximately 70% of patients with metastatic disease. These metastases can cause bone cells (osteoclasts) to become overactive, which can result in excessive bone loss, disrupting the bone architecture and causing skeletal-related events (SREs), such as fracture, the need for surgery or radiation therapy to bone, spinal cord compression and hypercalcemia of malignancy.
This document updates guideline recommendations that were first issued in 2000 and revised in 2003, and focused on the use of bisphosphonates. The current guideline uses the more inclusive term, bone-modifying agents, to reflect a wider category of therapeutic agents such as monoclonal antibodies that use different mechanisms of action to prevent and treat damage from bone metastases. The guideline notes that research remains to be conducted to address several areas where questions remain.
?The guideline considers new data in a variety of areas, including studies showing that denosumab has equivalent effectiveness compared with other currently available drug therapies,? explained bisphosphonates panel co-chair Jamie Von Roenn, MD, professor of medicine at Northwestern University. ?The guideline also provides guidance on preventing a rare, but significant complication of therapy with bone-modifying agents, osteonecrosis of the jaw.?
Denosumab is a human monoclonal antibody that targets a receptor, RANKL, involved in the regulation of bone remodeling. The guideline cites evidence from a randomized Phase III trial showing that denosumab appears to be comparable to zoledronic acid in reducing the risk of SREs in women with bone metastases from breast cancer. Denosumab is given subcutaneously, and can have side effects such as hypocalcemia.
The guideline also addresses the recently discovered osteonecrosis of the jaw. The first reports of this degenerative condition were published in the medical and dental literature in 2003. The committee recommended that all patients with breast cancer get dental evaluations and receive preventive dentistry care before beginning treatment with bone-modifying osteoclast inhibitors.
The panel updated its recommendations regarding the effects of bisphosphonates on kidney function, particularly for those taking either pamidronate or zoledronic acid, which have been associated with deteriorating kidney function. It said that clinicians should monitor serum creatinine clearance prior to each dose of pamidronate or zoledronic acid according to FDA-approved labeling.
The panel did not recommend using biochemical markers to monitor bone-modifying agent effectiveness and use outside of a clinical trial. While many of the 2003 recommendations remain the same, the guideline notes several research directions to be addressed, including:
- Duration of therapy with bone modifying agents, and the timing or intervals between delivery.
- The development of a risk index for SREs, and better ways to stratify patient risk of SRE or risk of toxicity from a bone-modifying agent. Individual risk may guide selection of timing for use of a bone-modifying agent therapy.
- Trials specifically examining whether stage IV breast cancer patients who do not have evidence of bone metastases would benefit from bone-modifying agents.
- The role of biomarkers in treatment selection and monitoring drug effectiveness.
- Understanding the optimal dosing of calcium and vitamin D supplementation in patients treated with bone-modifying agents.
For more information:
Van Poznak CH, Temin S, Yee GC, Janjan NA, Barlow WE, et al. American Society of Clinical Oncology Clinical Practice GuidelineUpdate on the Role of Bone-Modifying Agents in Metastatic Breast Cancer.