Arimidex® Associated with Fewer Side Effects than Tamoxifen

Arimidex® Associated with Fewer Side Effects than Tamoxifen.

According to results appearing in an early online publication from Lancet Oncology, treatment with Arimidex® (anastrozole) is associated with fewer side effects than treatment with tamoxifen (Nolvadex®).

Hormone-positive breast cancer is a common type of breast cancer. It is stimulated to grow with exposure to the female hormones estrogen and/or progesterone. Women with hormone-positive breast cancer are typically treated with hormone therapy, a type of therapy that reduces or prevents estrogen and progesterone from stimulating the growth and spread of cancer cells. Hormone therapy reduces the risk of a cancer recurrence and improves cancer-free survival for patients with hormone-positive breast cancer.

The ATAC trial (anastrozole and tamoxifen, alone or in combination) was a large trial that compared Arimidex to tamoxifen (Nolvadex®) in postmenopausal women with early-stage, hormone-positive breast cancer. The agents Arimidex and tamoxifen are both used as hormone therapy to reduce the risk of recurrences in hormone-positive breast cancer.

Outcomes from the ATAC trial were superior among women treated with Arimidex compared to those treated with tamoxifen; researchers continue to update results periodically, and also continue to evaluate side effects associated with treatment with either of these agents.

Researchers affiliated with the ATAC trial recently reported results regarding long-term side effects of treatment with Arimidex or Nolvadex. The analysis included results collected during a follow-up of five years.

  • 61% of women treated with Arimidex experienced side effects from treatment, compared with 68% of women treated with tamoxifen.
  • Serious side effects related to treatment occurred in 5% of women treated with Arimidex, compared with 9% treated with tamoxifen.
  • Therapy that was withdrawn due to side effects of treatment that occurred in 11% of women treated with Arimidex, compared with 14% of women treated with tamoxifen.
  • Women treated with tamoxifen had a greater risk of blood clots and uterine cancers, while women treated with Arimidex had a greater risk of decreased bone density and bone fractures.

The researchers concluded that these results provide further evidence that Arimidex may be a superior treatment to tamoxifen to reduce the risk of cancer recurrences among postmenopausal women with early breast cancer. However, it is important for women with this disease to speak with their physician regarding their individual risks and benefits of treatment with either agent.

Reference: The Arimidex, Tamoxfen, Alone or in Combination (ATAC) Trialists’ Group. Comprehensive side-effect profile of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: long-term safety analysis of the ATAC trial. Lancet Oncology [early online publication]. July 19, 2006.

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