Breast cancer is the most common cancer in women (after skin cancer). A woman's risk for breast cancer is 1 in 8-10 and majority of women are diagnosed after the menopause.
Hormonal therapy (adjuvant therapy) is usually given after the operation, chemotherapy and/or radiotherapy for to those women who had estrogen receptor (ER) positive tumours. Both chemotherapy and some types of hormonal therapy speed up bone loss.
Tamoxifen has a beneficial effect on bone density in postmenopausal women but its clinical use is limited to five years.
Aromatase inhibitors (anastrozole, letrozole, exemestane) reduce the amount of oestrogen circulating in the body which may lead to osteoporosis. The risk of developing osteoporosis depends on how healthy the bones were before the breast cancer treatment. Women who had good bone density before breast cancer treatment are less likely to develop osteoporosis while on aromatase inhibitor (AI) treatment than those who already had low bone density.
Women who are at particularly high risk of experiencing negative effect of AI on their bone health are recently menopausal (within four years of menopause), who previously had chemotherapy and who previously had low bone density (BMD). Other factors which increase risk of developing osteoporosis while on AI are: previous fracture, family history of hip fracture, being thin, smoking, having three or more alcoholic drinks per day, steroid treatment and certain diseases such as rheumatoid arthritis.
Bone loss in women on AI appears to be continuous (while a woman is on therapy) with and increased risk of low trauma fracture of about 50%. However, recent data suggest that after discontinuation of treatment this bone loss is reversible.
Both bisphosphonates (alendronic acid, risedronate, pamidronate and zoledronic acid) and denosumab are potent inhibitors of bone resorption and are highly effective in preventing bone loss induced by AI.
Any woman with breast cancer who has had low trauma fracture or is postmenopausal or on AI therapy should have DXA scan to asses BMD. If her T-score is below -2.0 treatment with bisphosphonate or denosumab should be initiated in addition to basic preventive measures. The basic preventive measures are: calcium intake of 1 - 1.5 g daily, optimizing vitamin D level (usually achieved by taking 1000 - 2000 IU of vitamin D daily) and weight-bearing and muscle-strengthening exercise.