Cognitive Function Substudy - A substudy to the SOFT trial (ACTRN12605000416695) which evaluates the cognitive function of premenopausal women with endocrine responsive breast cancer participating in SOFT.

Prior to registration in the Co-SOFT substudy, all patients must be randomised to the SOFT (ACTRN12605000416695) parent trial. The SOFT trial is a phase III trial evaluating the role of ovarian function suppression and the role of exemestane as adjuvant therapies for premenopausal women with endocrine responsive breast cancer. Patients participating in the SOFT trial will be randomised to receive five years of tamoxifen (20mg orally daily), five years of tamoxifen (20mg orally daily) plus ovarian function suppression (via either GnRH analogue, surgical oophorectomy or ovarian irradiation) or five years of exemestane (25mg orally daily) plus ovarian function suppression (via either GnRH analogue, surgical oophorectomy or ovarian irradiation). The method of ovarian function suppression may be determined by the treating clinican/patient and may be altered during the five year period, if necessary. Patients may subsequently be registered to the Co-SOFT substudy, investigating cognitive function for patients participating in the SOFT parent trial. Cognitive function will be measured with a computerised test battery (CogState) consisting of computerised card games. Self reported cognitive function, psychological distress and fatigue will also be assessed via three multiple response based questionnaires.