Bone-targeted Therapy in Metastatic Breast Cancer

Metastatic breast cancer commonly involves the bones. This can be complicated by bone pain, fractures or high levels of calcium in the blood. Medications are commonly prescribed to help strengthen the bones and to prevent and treat these complications.

What medications are used for bone-targeted therapy in metastatic breast cancer?

The two types of medications used are bisphosphonates (such as zoledronic acid given monthly as an intravenous infusion, or ibandronate, a daily tablet), or denosumab (Xgeva), which is a type of monoclonal antibody given as a monthly injection under the skin.

Managing side effects of bone-targeted therapies

Common side effects to zoledronic acid or denosumab include: dizziness, rash, nausea, constipation, and flulike symptoms such as fatigue, headaches, muscle or joint pain, weakness, and fever. The side effects usually last 1-2 days however can persist for up to 10-12 days after your infusion.

Uncommon side effects include hypocalcaemia (low blood calcium levels), abnormal heart rhythm and impaired kidney function. Inflammation of the eye (uveitis, scleritis) can also occur uncommonly with zoledronic acid. Oral bisphosphonates (e.g. ibandronate) can cause irritation of the oesophagus, so care needs to be taken not to lie down for at least 30mins after taking these tablets.

Dental care and treatment with bisphosphonates

There is a small risk that taking any of these medications can lead to developing a jaw or tooth problem called osteonecrosis of the jaw (ONJ). This is typically associated with trauma to the jaw (e.g., tooth extractions), and is more likely to occur with higher doses of bisphosphonates given for longer periods of time.

The estimated risk in people having treatment with bisphosphonates or denosumab for metastatic breast cancer is ~2%. A dental review prior to commencing treatment is recommended to assess whether you are likely to need any major work (tooth extractions and other invasive dental procedures) in the foreseeable future. It is recommended to complete any dental work before commencing bisphosphonate or denosumab treatment.

Routine preventative dental check-ups are recommended every 6 months during treatment with bisphosphonate or denosumab treatment. Routine cleanings, fillings, and scaling do not appear to increase the risk of osteonecrosis.