Effect of Tamoxifen on Bone Mineral Density

Effects in Postmenopausal Women

The National Comprehensive Cancer Network (NCCN) notes that tamoxifen acts as an estrogen agonist on bone tissue in postmenopausal women with typically lower estrogen levels, resulting in increased bone mineral density 1, 2
In postmenopausal women with breast cancer, tamoxifen is associated with preservation of bone mineral density and reduced fracture risk 3
The American College of Clinical Oncology recommends that for postmenopausal women with breast cancer, tamoxifen provides a beneficial effect on bone health in addition to its anti-cancer properties 6, 1

The National Comprehensive Cancer Network (NCCN) panel notes that in premenopausal women, tamoxifen may oppose the more potent effects of estrogen on bone and potentially increase the risk for osteoporosis 1, 2
Tamoxifen taken for 3 years by premenopausal women has been associated with bone loss 4, 5
Despite the potential for bone loss, the National Comprehensive Cancer Network (NCCN) panel does not recommend monitoring of bone mineral density in premenopausal patients on tamoxifen, as development of osteopenia/osteoporosis in this population is considered unlikely 1, 2

The American College of Clinical Oncology notes that when comparing treatment options, tamoxifen has a more favorable effect on bone mineral density than aromatase inhibitors, which are associated with increased bone loss and fracture risk 9, 3
In the ATAC trial, anastrozole significantly increased fracture risk compared with tamoxifen (7.1% vs 4.1%) after a mean of 37 months follow-up 3

For postmenopausal women on tamoxifen, routine bone density monitoring is not necessary due to the bone-preserving effects 1, 2
For premenopausal women who develop chemotherapy-induced menopause while on tamoxifen, bisphosphonates may be considered as one of several potential options for preservation of bone density 8
For women transitioning from tamoxifen to aromatase inhibitors, monitoring bone health becomes more important due to the increased risk of bone loss with aromatase inhibitors 3