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Adjuvant tamoxifen associated with reduced 15-year risk for breast cancer recurrence, death
Early Breast Cancer Trialists’ Collaborative Group. Lancet. 2011;doi:10.1016/S0140-6736(11)60993-8.
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Five years of treatment with adjuvant tamoxifen “substantially” reduced the 15-year risk for breast cancer recurrence and death, according to results from a patient-level meta-analysis of 20 randomized trials.
Data on 21,457 women were included in the study; half assigned to 5 years of tamoxifen and half to control.
Tamoxifen reduced the recurrence rate by half in women with ER-positive disease in years 0 to 4 after randomization and by one-third in years 5 to 9. There was little further effect after year 10. Researchers said the risk for recurrence decreased an average of 39% (RR=0.61) and for contralateral disease incidence (RR=0.62) over all time periods.
Researchers did not observe a beneficial effect on any recurrence (RR=0.97 for any recurrence; 95% CI, 0.88-1.07) or contralateral recurrence (RR=0.94; 95% CI, 0.73-1.20) for patients with ER-negative disease.
For patients with ER-positive disease, the yearly rate of breast cancer mortality declined by roughly a one-third (RR=0.70) throughout the first 15 years after randomization with a highly significant extra benefit during each 5-year period: 0 to 4 years (RR=0.71; 95% CI, 0.62-0.80), 5 to 9 years (RR=0.66; 95% CI, 0.58-0.75) and 10 to 14 years (RR=0.68; 95% CI, 0.56-0.83).
Because tamoxifen delayed or prevented recurrence, patients assigned to tamoxifen had more time at risk of death without recurrence (56,747 woman-years vs. 48,876 woman-years). Therefore, absolute numbers of deaths before recurrence are not directly comparable between control and experimental groups, but researchers said log-rank analyses make due allowance for this imbalance.
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