Five versus more than five years of tamoxifen for lymph node-negative breast cancer: Updated findings from the National Surgical Adjuvant Breast and Bowel Project B-14 randomized trial

Background: Previously reported information from B-14, a National Surgical Adjuvant Breast and Bowel Project (NSABP) randomized, placebo-controlled cl inical trial, demonstrated that patients with estrogen receptor (ER)-positi ve breast cancer and negative axillary lymph nodes experienced a prolonged benefit from 5 years of tamoxifen therapy, When these women were rerandomiz ed to receive either placebo or more prolonged tamoxifen therapy, they obta ined no additional advantage from tamoxifen through 4 years of follow-up. B ecause the optimal duration of tamoxifen administration continues to be con troversial and because there have been 3 more years of follow-up and a subs tantial increase in the number of events since our last report, an update o f the B-14 study is appropriate. Methods: Patients (n = 1172) who had compl eted 5 years of tamoxifen therapy and who were disease free sere rerandomiz ed to receive placebo (n = 579) or tamoxifen (n = 593), Survival, disease-f ree survival (DFS), and relapse-free survival (RFS) were estimated by the K aplan-Meier method; the differences between the treatment groups were asses sed by the log-rank test. Relative risks of failure (with 95% confidence in tervals! were determined by the Cox proportional hazards model. P values we re two-sided. Results: Through 7 years after reassignment of tamoxifen-trea ted patients to either placebo or continued tamoxifen therapy, a slight adv antage was observed in patients who discontinued tamoxifen relative to thos e who continued to receive it: DFS = 82% versus 78% (P =.03), RFS = 94% ver sus 92% (P =.13), and survival = 94% versus 91% (P =.07), respectively. The lack of benefit from additional tamoxifen therapy was independent of age o r other characteristics. Conclusion: Through 7 years of follow-up after rer andomization, there continues to be no additional benefit from tamoxifen ad ministered beyond 5 years in women with ER-positive breast cancer and negat ive axillary lymph nodes.