Adjuvant Bisphosphonates for Early Breast Cancer
In postmenopausal women with early breast cancer, bisphosphonates have been demonstrated to reduce the risk of recurrence of cancer in the bones, as well as improving overall survival outcomes.
What are bisphosphonates?
Bisphosphonates are a group of medicines usually used to treat bone problems such as osteopenia or osteoporosis. In postmenopausal women with early breast cancer, some of these medicines have also been demonstrated to reduce the risk of recurrence of cancer in the bones, as well as improving overall survival outcomes.
Bisphosphonates and early breast cancer treatment
The American Society of Clinical Oncology (ASCO) now recommends that adjuvant treatment with bisphosphonates should be considered for postmenopausal women with breast cancer who have received adjuvant chemotherapy. This is based on evidence from multiple studies, as well as an analysis of pooled data conducted by the Early Breast Cancer Trialists’ Collaborative Group [EBCTCG].
The main benefit of using bisphosphonates in early breast cancer treatment is to reduce the risk of recurrence and improve survival. A secondary benefit for some women is to offset the effect of hormonal treatments on bone density.
Zoledronic acid – how does it work?
For most postmenopausal women receiving chemotherapy for early breast cancer, Dr Forster recommends considering zoledronic acid treatment for 3 years. This is administered by an intravenous infusion every 6 months.
Currently, zoledronic acid is not covered by the PBS for this indication. Generic brands cost approximately $100-$150 per dose. You may be able to claim some of this back from your private health fund if you have ‘extras’ cover for pharmaceuticals.
Side effects from using Zoledronic acid
Common side effects to zoledronic acid include:
dizziness, rash, nausea, constipation
flu-like symptoms such as fatigue, headaches, muscle and joint pain, weakness, and fever
These side effects usually last 1-2 days however can persist for up to 10-12 days after your infusion
Uncommon side effects to zoledronic acid include:
hypocalcaemia (low blood calcium levels)
abnormal heart rhythm
impairment of kidney function
inflammation of the eye (eg uveitis, scleritis)
There is a small risk with zoledronic acid of developing a jaw or tooth problem called osteonecrosis of the jaw (ONJ). This is typically associated with trauma to the jaw (eg 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 adjuvant bisphosphonates is ~1%.
A dental review prior to commencing treatment is recommended to see if any major work (tooth extractions and other invasive dental procedures) is needed in the foreseeable future. It is recommended to complete any dental work before commencing bisphosphonate treatment. The risk of ONJ persists after completing bisphosphonate treatment, perhaps for some years. Routine preventative dental check-ups are recommended every 6 months during adjuvant zoledronic acid treatment and for several years afterwards. Routine cleanings, fillings, and scaling do not appear to increase the risk of osteonecrosis.
To assist with bone health and in view of the risk of zoledronic causing low calcium levels, supplementation with calcium (calcium carbonate 600mg daily ) and vitamin D (1000IU daily) is recommended for the duration of the time you are receiving treatment.