Adjuvant tamoxifen - longer against shorter

INTERVENTION: Patients enter the trial after completing approximately 5 years of tamoxifen for early breast cancer and are randomised to either continue tamoxifen for a further 5 years or stop tamoxifen. The dosage of tamoxifen is recommended at 20mg.day orally unless the patient's clinician prefers a different dosage. Patients will continue to be followed for at least 5 years after completing treatment. CONDITION: Early Breast Cancer PRIMARY OUTCOME: The aim of ATLAS is to compare different durations of adjuvant tamoxifen therapy for early breast cancer to determine the optimum duration based on the evaluation of: ; * All cause mortality ; * Cause specific mortality (including breast cancer, myocardial infarct, and other cancers) ; * Non fatal events (including new, contralateral primary breast cancer, other cancers, myocardial infarct and other vascular events requiring hospitalisation) SECONDARY OUTCOME: N/A INCLUSION CRITERIA: Women who have received any type of curative surgery for early breast cancer are eligible (irrespective of the original histological type of the disease, nodal status, or whether the tumour was estrogen receptor positive or negative) so long as the woman appears currently to be free of breast cancer and is receiving tamoxifen and where both the woman and her doctor are uncertain whether to continue with tamoxifen.