Randomized Trial of Two Versus Five Years of Adjuvant Tamoxifen for Postmenopausal Early Stage Breast Cancer

• Published in: JNCI Journal of the National Cancer Institute
• Main Author: Swedish Breast Cancer Cooperative Group
• Format: Text
• Language: English
• Published: Oxford University Press 1996
• Subjects: ARTICLES; North Sweden
• Online Access: http://jnci.oxfordjournals.org/cgi/content/short/88/21/1543; https://doi.org/10.1093/jnci/88.21.1543

Background : Postsurgical treatment with tamoxifen has been shown to improve overall survival among patients with early stage breast cancer. However, the optimal duration of tamoxifen treatment remains controversial. Purpose : A multicenter, randomized trial was initiated in Sweden in the early 1980s to compare 2 years with 5-years of adjuvant tamoxifen in the treatment of postmenopausal women younger than 75 years of age who had early stage, axillary lymph node-negative or -positive, invasive disease. Methods : The trial was planned and organized by the Swedish Breast Cancer Group, and it involved five regional breast cancer study organizations (South Sweden, South-East Sweden, Stockholm, Uppsala-Örebro, and North Sweden). During the period from 1983 through 1991, a total of 3887 patients were entered in the trial; 3545 (91%) women remained alive and recurrence free at 2 years and could thus contribute meaningful information to the 2-year (n = 1801) versus 5 year (n = 1744) comparison. Primary surgery consisted of either modified radical mastectomy or breast-conserving surgery. Radiation therapy was indicated for patients with lymph node-positive disease and was generally offered to all women who were treated with breast-conserving surgery. Only 89 (2.5%) of the 3545 women who were recurrence free at 2 years received adjuvant chemotherapy concurrently with tamoxifen. Twenty-milligram daily doses of tamoxifen were used at two centers, and 40-mg daily doses were used at the remaining three centers. Estrogen receptor status of the tumor was known for 2987 women (77% of the entered patients). Primary end points in the trial were event-free survival (local-regional recurrence, distant metastasis, contralateral breast cancer, or death) and overall survival. Survival curves were estimated by use of the life-table method. The Cox proportional hazards model was used to make comparisons between the 2- and 5-year treatment groups. Results : Patients assigned to receive 5 years of tamoxifen, compared with 2 years of ...