Zoledronic acid is a medication used to manage various bone conditions by influencing bone turnover. It is particularly important in breast cancer treatment due to its effects on bone health.
What Zoledronic Acid Is
Zoledronic acid belongs to the bisphosphonate class of drugs. It interacts with bone tissue to slow down the rate at which old bone is removed from the skeletal system. This action helps maintain and potentially increase bone density, contributing to overall bone strength.
Why It’s Used in Breast Cancer
Zoledronic acid plays several important roles in breast cancer management, especially for bone health. It is primarily used to prevent or treat bone metastases, where cancer cells spread to the bones. For patients with bone metastases, it reduces skeletal-related events (SREs) like pathological fractures, spinal cord compression, and hypercalcemia (high blood calcium).
The medication also counteracts bone loss caused by certain breast cancer treatments, such as aromatase inhibitors (AIs). AIs, prescribed for postmenopausal women with hormone receptor-positive breast cancer, can accelerate bone density loss and increase fracture risk. Zoledronic acid helps preserve bone mineral density in these patients.
Beyond managing existing bone issues, zoledronic acid has an adjuvant role in some breast cancer treatment plans. For postmenopausal women with early breast cancer, especially with lymph node involvement, it can reduce the risk of bone recurrence. Studies show it can improve disease-free survival in specific patient groups.
How Zoledronic Acid Works
Zoledronic acid works by targeting and inhibiting osteoclasts, the cells responsible for breaking down bone tissue. It binds to the mineral surfaces of bone, especially where bone remodeling is active. When osteoclasts absorb the bound zoledronic acid, it interferes with a crucial biochemical pathway within them. This disruption impairs osteoclast function and survival, reducing their ability to resorb bone. By slowing bone breakdown, zoledronic acid helps maintain existing bone structure and preserves bone density.
Receiving Treatment and Managing Effects
Zoledronic acid is administered intravenously, directly into a vein. The infusion typically takes at least 15 minutes. Frequency varies, but it’s commonly given every three to four weeks initially, or every three to six months for ongoing therapy. Patients usually receive treatment in an outpatient setting.
Patients may experience side effects, especially after initial infusions. Common temporary symptoms include flu-like symptoms, bone or muscle pain, headaches, and nausea. These usually resolve within 24 to 48 hours. To manage potential low blood calcium, patients may be advised to take calcium and vitamin D supplements.
A more serious, though rare, side effect is osteonecrosis of the jaw (ONJ), where jaw bone tissue can become damaged and exposed. The risk of ONJ is generally low, but higher in patients with metastatic breast cancer. Factors increasing this risk include prolonged use of the medication, higher doses, and existing dental or oral health issues. Patients are often advised to maintain good oral hygiene and inform their healthcare team and dentist to minimize this risk.
Kidney problems, including renal impairment or failure, can occur, especially in individuals with pre-existing kidney conditions or other risk factors. Healthcare providers will typically monitor kidney function by checking creatinine levels before each infusion. Ensuring adequate hydration before and after the infusion is also important to help protect kidney health during treatment. In rare instances, long-term use of zoledronic acid has been associated with atypical fractures of the thigh bone.