Bone-directed therapy for breast cancer is used in two major settings:
- As an adjuvant therapy after surgery to reduce the risk of cancer recurrence
- In stage 4 disease when breast cancer has spread to bones
Bone-directed therapy as an adjuvant therapy after surgery:
Breast cancers can sometimes recur and spread to bones, usually many years after patients have had an operation to remove the breast cancer. Studies showed that when Bisphosphonate is added to standard adjuvant therapy (chemotherapy and endocrine therapy) after breast cancer surgery, it can reduce the risk of breast cancer recurrence in the future. This treatment is suitable for patients who are menopausal (or in premenopausal age but taking treatment to suppress their ovaries).
Bisphosphonates are a group of medications that are commonly used to treat osteoporosis (thin bones). They act by increasing bone density and subsequently their strength to reduce the risk of fractures.
The Bisphosphonates drug that is used in this sitting is Zoledronic acid. It is given through a drip into a vein over 10 – 15 minutes once every 6 weeks while on chemotherapy and once every 6 months for 3 years following chemotherapy.
Some people may experience flu-like symptoms (like fever, aching muscles or a headache) for few days following the infusion. This can be managed by mild painkillers, such as paracetamol or ibuprofen if required.
Occasionally, Bisphosphonate can cause osteonecrosis of the jawbone (ONJ) where the jawbone begins to weaken and die causing pain sometimes. Most cases of osteonecrosis of the jaw happen after a dental extraction in patients receiving Bisphosphonate treatment. Patients on this treatment are strongly advised to have a full dental assessment before they start treatment and regular dental check-ups while on treatment. They should not have non-emergency dental work done 6 weeks before or after an infusion. Good oral hygiene and regular dental care is the best way to lower the risk of ONJ.
Bone-directed therapy in stage 4 disease when breast cancer has spread to bones:
A large number of breast cancers can be cured but some may spread to other organs like liver, lungs, bone and brain. This is called a stage 4 Breast cancer (and sometimes called metastatic or secondary breast cancer). When breast cancer spreads to bones it can make them weak and prone to fracture easy. Bone-directed therapy is used in this case to increase the density of bone, make them stronger and reduce the risk of fractures in the future. The drugs used are either Bisphosphonate or Denosumab.
Bisphosphonates: In stage 4 breast cancer they may be given orally (like Aledronic acid) daily or once weekly, or through a drip (like Zoledronic acid once every 4 weeks).
Denosumab has been found to be more effective than bisphosphonate in a large clinical study published in 2012. It is given once every four weeks continuously as an injection under the skin. The most common side effects are joint and muscle pain. Denosumab may also cause osteonecrosis of the jawbone and patients are strongly advised to have a full dental assessment before they start treatment and regular dental check-ups while on treatment. They should not have non-emergency dental work done 6 weeks before or after an injection. Good oral hygiene and regular dental care is the best way to lower the risk of ONJ.