Cancerbackup: Summary of trials

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Summary of trials for aromatase inhibitors in early breast cancer

All the trials mentioned have looked at different aromatase inhibitors, given using different schedules.

In the adjuvant setting, the aromatase inhibitors are proving to be an improvement on tamoxifen alone in terms of reducing breast cancer events. When all the aromatase inhibitor studies are combined and compared with the current standard of five years of tamoxifen, incorporating aromatase inhibitors either as initial treatment, switching after two to three years of tamoxifen or giving an aromatase inhibitor after five years of tamoxifen have been shown to increase disease free survival.


Side effects of tamoxifen

The side effects of tamoxifen include hot flushes and sweats, nausea and weight gain. Generally tamoxifen is well tolerated. Tamoxifen also has some long term side effects; in particular there is an increased risk of developing endometrial cancer with prolonged use of tamoxifen. There is also, a risk of thromboembolic disorders. However, tamoxifen also has benefits, in that it protects against bone loss in post menopausal women, thus reducing the risk of osteoporosis.


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Side effects of aromatase inhibitors

The short term side effects of aromatase inhibitors include hot flushes and sweats, vaginal dryness, joint pains and stiffness, nausea, and fatigue. However, these tend to be low grade and are generally well tolerated. According to current experience, there is less likelihood of thromboembolic events and gynaecological side effects. There may be a greater chance of developing osteoporosis.

There is limited information about any long-term side effects of aromatase inhibitors. A drop in bone mineral density has been demonstrated in several trials and is a class effect of aromatase inhibitors rather than limited to a specific drug. Managing the impact on bone density is another issue to be considered (4) The ASCO bisphosphonates guidelines suggest that a baseline bone mineral density (DEXA) scan should be carried out before taking aromatase inhibitors for women at high risk of osteoporosis (11).

Limited information is available about possible cardiovascular effects from aromatase inhibitors and this will also need to be monitored.


Content last reviewed: 01 July 2006
Page last modified: 19 April 2007

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