Materials and methods
Breast Cancer, tumors, breast cancer
BREAST CANCER, TUMORS, INVASIVE BREAST CANCER, BREAST CANCER
The trial was planned and organized by the Swedish Breast Cancer Group and involved five regional breast cancer centers and was approved by their Ethics Committees. Study characteristics by trial center are shown in Study characteristics by trial center.During the period 1983–1992 a total of 4610 postmenopausal women younger than 75 years with stage I to IIIA invasive breast cancer were entered into a randomized trial comparing five and two years of adjuvant tamoxifen. Mean age at treatment start was 62.7 years in the two-year group and 62.6 in the five-year group. Twenty milligrams daily doses were used at two centers, and 40 mg daily doses at the remaining three centers. The treatment was given regardless of ER status but most tumors had ER determined with isoelectric focusing or Abbot enzyme immunoassay as previously described [Consort diagram.