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Alternative breast cancer drug shows promise

BMJ 2005; 331 doi: (Published 11 August 2005) Cite this as: BMJ 2005;331:368

This article has a correction. Please see:

  1. Allison Barrett
  1. BMJ

    The drug anastrozole (Arimidex) is more effective at inhibiting breast cancer recurrence than tamoxifen, a study published in the Lancet has found (2005;366:455-62). Researchers in Austria and Germany studied 3200 postmenopausal women who had received two years of tamoxifen, the current first line drug treatment for women with hormone responsive breast cancer. One randomised group continued receiving tamoxifen (1606 women), and the other took anastrozole alone (1618 women).

    After a two year follow-up, the anastrozole group had 40% fewer events, defined as local recurrence, distant recurrence, or contralateral breast cancer. The tamoxifen group had 110 events, while the anastrozole group had 67 (hazard ratio 0.60, 95% confidence interval 0.44 to 0.81; P=0.0009). Women taking anastrozole experienced more bone fractures but fewer blood clots.

    Coauthor Raimund Jakesz of the Vienna Medical University said, “Although further investigation is necessary to ascertain the ideal sequence and duration of adjuvant endocrine therapy, this combined analysis confirms that postmenopausal women who receive tamoxifen as adjuvant therapy should be switched to anastrozole after two years of treatment.”

    Emma Taggart, director of policy and campaigns for Breakthrough Breast Cancer in the UK, said, “This is welcome news. Tamoxifen has already made a big impact in reducing the risk of recurrence for certain breast cancer patients but Arimidex can also make a real difference. We look forward to further research on how long, and in what order, these drugs should be used.”

    Anastrozole, given as a 1 mg tablet daily, is an aromatase inhibitor that decreases oestrogen synthesis, and tamoxifen is an oestrogen analogue. Both work best on oestrogen receptor positive tumours. Tamoxifen, now available in generic forms, is much cheaper at £2.24 ($4.00; £3.24) for a 30 pack of 20 mg tablets compared with £68.56 for a 28 pack of 1 mg anastrozole tablets. Current clinical guidelines recommend tamoxifen (20-30 mg daily) for five years after diagnosis of oestrogen receptor positive breast cancer.

    In the United States, anastrozole is approved for postmenopausal women as a first line treatment for early breast cancer and advanced breast cancer, and adjuvant treatment for early breast cancer. In the United Kingdom it is licensed only for treating women who are unable to take tamoxifen.

    The National Institute for Clinical Excellence (NICE) is currently reviewing hormonal treatments for breast cancer. The timeline for their review will not be changed nor the drug fast tracked as a result of the new data, said a NICE spokeswoman. Their review should be published in November 2006.

    “We hope that NICE will take steps to ensure that the drug is available to all who could benefit from it as quickly as possible,” said Ms Taggart.

    This study follows the ATAC (Arimidex, tamoxifen, alone or in combination) trial (Lancet 2002;359:2131-9). This showed that five years of adjuvant anastrozole was superior to tamoxifen in preventing recurrence in postmenopausal oestrogen receptor positive women with early breast cancer. Fractures were higher in the anastrozole group, but the drug was generally better tolerated than tamoxifen.

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