OUTLINE: This is a randomized study. Patients are stratified for analysis according to duration of tamoxifen given before randomization (2-3 years vs 4-5 years vs 6-7 years vs 8-9 years vs 10 years and over), age (less than 49 vs over 50), and important prognostic factors, including tumor type and grade and nodal and estrogen receptor status. Patients are randomized to 1 of 2 treatment arms.