Bone Protective Therapy in Breast Cancer Patients
Bone health is very important for breast cancer patients because pre-menopausal women who get chemotherapy in the adjuvant setting will have ovarian failure almost 90% of the time, which will lead to osteopenia and bone loss. Post-menopausal women ER/PR positive often time will have as part of standard care aromatase inhibitors, which are also associated with bone loss and osteoporosis increase in the risk for fractures.
Also, pre-menopausal patients may be receiving hormonal therapy coupled with GNRH (gonadotropin releasing hormone), which causes chemical suppression of the ovaries and are at increased risk of osteopenia/osteoporosis.
Nowadays, several drugs have been FDA approved to prevent or reverse bone loss. The initial oral bisphosphonates, which were FDA-approved, were not very popular because of frequent gastrointestinal problems.
Intravenous zolendronic acid (Reclast) was better tolerated but in ~2% of cases could cause osteonecrosis of the jaw in particular if dental trauma occurs or if patients have poor oral hygiene. Reclast is an intravenous bisphosphonate given once a year. The infusion is less than one hour. It inhibits osteoclastic bone resorption. The calcium level needs to be checked prior to treatment and if low, calcium and vitamin D to be supplemented.
Prolia (denosumab) could cause an allergic reaction. It reduced the risk of fracture 66% compared to placebo. The rank ligand inhibitor (denosumab) a subcutaneous injection given every six months revealed increased bone mineral density and decrease in bone fracture. Calcium and vitamin D are given as supplements.
It appears that bisphosphonate therapy has an antitumor effect as well, increasing disease-free survival and overall survival in post-menopausal women while reducing the incidence of fractures.
In patients with metastatic disease to the bones, zolendronic acid (Zometa) is given monthly at a dose of 4mg and denosumab (Xgeva) is also given monthly at a dose of 120mg. All bone protective agents have greatly decreased the incidence of fractures.