POSTCHEMOTHERAPY ADJUVANT TAMOXIFEN THERAPY BEYOND 5 YEARS IN PATIENTS WITH LYMPH NODE-POSITIVE BREAST-CANCER

Background: Data from a pilot study published in 1984 suggested that t amoxifen administration (as adjuvant hormonal therapy) for more than 5 years after initial breast cancer surgery might have therapeutic bene fit. Purpose: A randomized trial was performed to assess the efficacy of maintaining tamoxifen therapy beyond 5 years in women with axillary lymph node-positive breast cancer who had been treated with surgery f ollowed by 1 year of chemotherapy and 5 years of tamoxifen. Methods: O ne hundred ninety-four women (87 postmenopausal and 107 premenopausal) enrolled in two concurrent Eastern Cooperative Oncology Group adjuvan t trials (E4181 for postmenopausal patients and E5181 for premenopausa l patients) were randomly assigned to continued tamoxifen therapy or o bservation. Data for 193 women (87 postmenopausal and 108 premenopausa l) were available for analysis. Median follow-up being 8.0 years. The major analyses measured events from the time of randomization until re lapse or death; these include time-to-relapse analyses, with new oppos ite-breast cancers counted as treatment failures, and survival analyse s. Time-to-relapse comparisons and survival comparisons for women in t he two treatment groups were made by use of the Kaplan-Meier method an d the log rank test. Reported P values are two-sided. Results: Five ye ars after the randomization , no statistically significant differences were noted in either time to relapse or survival between women contin uing to receive tamoxifen and those on observation. Eighty-five percen t of the women receiving tamoxifen were disease free at this time comp ared with 73% of those on observation (P=.10); survival was 86% for th ose continuing to receive tamoxifen and 89% for those on observation ( P=.52). Differences in the time to relapse and survival between premen opausal and postmenopausal women assigned to the two treatment groups were also not statistically significant (time to relapse: P=.38 and P= .16 for premenopausal and postmenopausal patients, respectively; survi val: P=.18 and P=.72 for premenopausal and postmenopausal patients, re spectively). There was an indication that women with estrogen receptor -positive tumors may experience a longer time to relapse with continue d tamoxifen therapy (P=.014); however, the survival difference for thi s subgroup was not statistically significant (P=.81). The toxicity pat terns in the two treatment groups were similar. Conclusions and Implic ations: Our results suggest that further evaluation of adjuvant tamoxi fen therapy beyond 5 years in women with axillary lymph node-positive, estrogen receptor-positive breast cancer who have also been treated w ith adjuvant chemotherapy would be appropriate.