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Practice ABC of breast diseases

Medical treatment of early breast cancer. II: endocrine therapy

BMJ 2006; 332 doi: (Published 12 January 2006) Cite this as: BMJ 2006;332:101
  1. Ian Smith, professor of cancer medicine,
  2. Susan Chua, medical oncologist
  1. Royal Marsden Hospital, London
  2. Melbourne, Australia

    Choice of adjuvant treatment depends on risk of relapse, potential benefits of different treatments, oestrogen receptor status, age of the patient, and acceptability of treatment to the patient. The risk of relapse relates to known prognostic factors, and these can be used to define risk groups. Age and menopausal status are important factors that influence the choice of adjuvant treatment.

    Endocrine treatment

    Until recently tamoxifen was the most commonly used hormonal agent in the adjuvant setting in premenopausal and postmenopausal women. A major development in adjuvant treatment for early breast cancer in postmenopausal women has been the emergence of the so called third generation aromatase inhibitors (anastrozole, letrozole, and exemestane), with increasing evidence of their superiority to tamoxifen.

    Disease free survival in women with oestrogen receptor positive in the study of adjuvant anastrozole, tamoxifen, or the combination (ATAC). Curves are truncated at 42 months. Adapted from Lancet 2002; 359: 2131-9

    These drugs act by blocking the synthesis of oestrogen (which is mediated through the aromatase enzyme), in contrast to tamoxifen (which is an oestrogen receptor antagonist). Their efficacy has been established in postmenopausal women only. Anastrozole achieved a small but important disease free survival benefit (3.3% improvement at six years with a hazard ratio of 0.83 (95% confidence interval 0.73 to 0.94) in the hormone receptor positive group compared with tamoxifen or the combination in the large ATAC (Arimidex, tamoxifen, alone or in combination) trial. Patients treated with anastrozole also had a small but significant reduction (0.86, 0.74 to 0.99) in distant disease free survival, but the latest analysis at 68 months showed no overall survival difference. Data from the Breast International Group 1-98 (BIG 1-98) study compared letrozole with tamoxifen in 8028 women with a median follow-up period of 25.8 months, and showed that patients who received immediate treatment with letrozole …

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