Bisphosphonates are an important class of therapeutic agents for breast cancer patients who present with bone metastases. What conditions can this class of drugs be used for and how are they applied?
What are the effects of bisphosphonates?
There are three generations of bisphosphonates, and Zoledronic Acid and Ibandronic Acid are third-generation drugs that can effectively suppress bone complications from metastases, as well as prevent and treat disease-related bone loss, maintain bone density, and treat malignant hypercalcemia to improve survival.
For patients with bone metastases from breast cancer, zoledronic acid is 92.3% effective in relieving cancer pain with few adverse effects and has been recommended by the American Society of Clinical Oncology, (ASCO) as a first-line treatment for bone metastases.
When to use bisphosphonates?
Currently, the primary goal of using bisphosphonates in patients with bone metastases from breast cancer is to reduce the incidence of bone-related events.The following five categories of patients are recommended for bisphosphonates in the 2017 Chinese Anti-Cancer Society Guidelines and Specifications for the diagnosis and treatment of breast cancer.
- Bone metastases causing hypercalcemia.
- Bone metastases causing hypercalcemia.
- Bone metastases causing bone pain.
- Bone metastases cause bone pain.
- Abnormal findings on bone radionuclide scan (ECT), X-ray or CT, magnetic resonance imaging (MRI) confirming bone metastases.
- Abnormal ECT findings, normal X-rays, but CT or MRI showing bone destruction.
- Imaging determines that there is bone destruction, even if there are no signs of bone pain.
How are bisphosphonates applied?
Current studies show that third-generation bisphosphonates are more effective, less toxic, and easier to use than the first two generations of bisphosphonates, and are most commonly used in the clinic.
It is important to note that before using a bisphosphonate, your doctor will order a blood test for electrolyte levels, focusing on blood creatinine, serum calcium, blood phosphorus, and magnesium.
Bisphosphonates can be used in combination with radiation therapy, chemotherapy, endocrine therapy, pain medications, and can be added to systemic therapy with zoledronic acid, ibandronate, pamidronate, or denosumab once a month. After 12 consecutive doses, if the disease is stable, the doctor will usually recommend a change to once every 3 months. People with severe renal insufficiency (creatinine clearance ≤30 ml/min) should inform their doctor, who will reduce the dose and duration of infusion as appropriate.
The risk of osteonecrosis of the jaw has been documented with long-term use of bisphosphonates, so before using bisphosphonates, the physician will recommend an oral examination and remind the patient to keep the mouth clean and avoid oral surgery, including tooth extraction, if possible, and to make sure to inform the dentist of the medication if intraoral procedures must be performed.
Patients with bone metastases from breast cancer can usually use bisphosphonates for a long time. However, it is best to take daily calcium (1200-1500 mg per day) and vitamin D (400-800 units per day) supplements for long-term use. If adverse reactions are found during the use of bisphosphonates and are clearly related to bisphosphonates, or if the tumor worsens or other organs metastasize during the treatment and becomes life-threatening, the doctor will usually recommend discontinuing the drug. However, relief of bone pain after other treatments is not a sign to discontinue bisphosphonates.
While bone metastases from breast cancer are advanced breast cancer, aggressive combination therapy and judicious use of bisphosphonates will still bring some improvement in outcomes. There are some considerations before and after the use of bisphosphonates that are important to keep in mind.