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Anastrozole Shows Superiority Over Tamoxifen in Early Breast Cancer Treatment

Strategic Insights

— 2 min read

A newly released set of data has highlighted the importance of the initial treatment decision for women with early breast cancer, specifically the choice between anastrozole and tamoxifen. The study, presented at ECCO 13 - The European Cancer Conference in Paris, France, found that women who were initially prescribed tamoxifen were at a higher risk of their cancer coming back and experienced more unpleasant gynaecological side effects, including vaginal discharge or bleeding to endometrial cancer.

Key Takeaways:

  • Women who were prescribed tamoxifen instead of anastrozole were at an increased risk of their cancer coming back, with a risk greatest in the first three years following surgery.
  • The ATAC trial data showed that women taking tamoxifen were almost four times more likely to have to undergo a hysterectomy as a result of gynaecological side effects.
  • Women taking tamoxifen experienced significantly more gynaecological side effects compared with anastrozole, with 34.2% experiencing side effects versus 20.5% in the anastrozole group (p = 0.0001).
  • The majority of gynaecological side effects experienced by women in the trial occurred during the first two and a half years of treatment.
  • Anastrozole is the only AI to have a full data-set over the standard treatment period of five years, confirming its superiority over tamoxifen in terms of efficacy and side effects.
  • A further study presented at ECCO this week revealed that anastrozole is the only AI with a side effect profile that has not raised concerns over cardiovascular safety compared with tamoxifen.

Statistics:

  • 34.2% of women taking tamoxifen experienced gynaecological side effects, compared with 20.5% of women taking anastrozole (p = 0.0001).
  • Women taking tamoxifen were almost four times more likely to have to undergo a hysterectomy as a result of gynaecological side effects.
  • The risk of cancer coming back was highest in the first three years following surgery for women taking tamoxifen.
  • More than five years of data are now available to compare the safety of anastrozole with tamoxifen in early breast cancer.

Sources:

  • Howell, A on behalf of the ATAC Trialists' Group. Global index to summarise health risks versus benefit in the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) trial. Abstract No: 349. Presented at ECCO 13, Paris, France
  • Duffy, S on behalf of the ATAC Trialists' Group. Gynaecological adverse events and hysterectomies in the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) trial. Abstract No: 268 Presented at ECCO 13, Paris, France
  • ATAC Trialists' Group. Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer. Lancet, 365 (9453): 60-62.
  • Nabholtz, J-M on behalf of the ATAC Trialists' Group. Comparison of cardiovascular safety profiles of aromatase inhibitors. Abstract No: 343 Presented at ECCO 13, Paris, France

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