Background: This study evaluated the impact on overall survival (OS) of 2 versus 5 years adjuvant tamoxifen in early breast carcinoma patients after 12 years of follow-up.
Methods: Women with breast carcinoma T1-3, N0-3, M0, aged 50-70 years, were eligible for this multicenter randomized Phase III trial. Patients event-free after 2 years of tamoxifen therapy (TAM) were randomly assigned to stop or continue TAM (20 mg/day) for an additional 3 years. The primary endpoint was disease-free survival. Secondary endpoints included OS and toxicity.
Results: From 1989 through 1996, 1901 patients were randomly assigned either to stop treatment (n = 958) or to continue TAM (n = 943). Overall, 98% of patients alive at the previous report (n = 1611) had updated information about OS, of whom 549 had died. The median duration of postrandomization follow-up was 115 months (interquartile range, 86-137). No statistically significant differences between the two arms were detected in the whole population (hazard ratio [HR], 1.02; 95% confidence interval [CI], 0.86-1.22) and in estrogen receptor (ER)-positive patients (HR, 0.90; 95% CI, 0.72-1.13). In the latter group, survival curves started to diverge after 90 months, showing a trend in favor of the 5-year arm. In younger (age < or =55 yrs) ER-positive patients longer TAM was associated with a 44% decrease in the risk of death (HR, 0.56; 95% CI, 0.31-1.00), while no clear benefit was documented in women older than 55 years of age (HR, 0.98; 95% CI, 0.77-1.25).
Conclusions: The benefits of longer TAM on OS start to emerge only after 9 years from diagnosis and seem to be more relevant in younger ER-positive women.