New data from a five-year update from the bone sub protocol of the ATAC trial confirm that women who have a normal bone mineral density (BMD) at the outset of treatment may be able to undergo a five-year course of therapy with Arimidex (anastrozole) without the risk of developing osteoporosis.
These trial results, a subset of data from one of the world's longest running and largest studies of breast cancer treatment after surgery, were presented at the American Society for Clinical Oncology (ASCO) annual meeting.
The results of this study indicate that a reduction in BMD does occur over the five-year course of treatment with Arimidex, although there appeared to be a slowing down of the rate of bone loss in the lumbar spine in years two to five. These study results provide additional evidence that bone adverse events are predictable and may be manageable, with proper monitoring, for Arimidex.
The impact of aromatase inhibitors, such as Arimidex, on BMD has been an important clinical question for physicians and breast cancer patients alike. In addition, recent treatment guidelines also highlighted that additional evidence was needed regarding the effect of aromatase inhibitors on bone strength. These results provide further support for current guidelines the use of aromatase inhibitors, such as Arimidex, for the treatment of early breast cancer in postmenopausal women, specifically in patients with normal baseline BMD.
The majority of the women in the ATAC trial have now completed their five years of treatment, so the data from this bone sub protocol reflect the benefits and risks of a complete course of treatment with Arimidex. Data this mature does not exist for any other aromatase inhibitor.