Skeletal effects of drugs to treat cancer

Drugs used to treat cancer may affect the skeleton in several ways, the most important being a decrease in sex steroid levels. This may induce rapid bone loss. Tamoxifen is a partial oestrogen receptor agonist and antagonist (classified as a selective oestrogen receptor modulator or SERM). As it has agonistic effects on oestrogen receptors of bone it increases bone mineral density and thus may potentially prevent fractures. In contrast aromatase inhibitors such as anastrozole lead to a decrease in bone mineral density and an increased risk of fractures. Most high-dose intravenous chemotherapeutic regimens induce rapid bone loss from effects on the gonads with induction, for example, of premature menopause. Low-dose oral agents such as methotrexate are not associated with an increased risk of fractures. Androgen deprivation therapies such as LHRH agonists in breast cancer are also associated with an increase in bone loss and an increased risk of fractures. With the increasing long-term survival of patients with cancer, preventive measures against osteoporosis must be considered.