Cognitive Sequelae of Adjuvant Endocrine Therapy for the Treatment of Breast Cancer in Older Women

The convenience sample will consist of chemotherapy-naïve women 65 and older with a first diagnosis of early stage HR+ BC, post surgical resection, who are prescribed either TAM (n=25) or an AI, anastrozole or letrozole (n=50). Based on a survey of medical oncologist prescribing practices at Sunnybrook, the investigators will be able to obtain sufficient numbers for the convenience sample from the pool of 220 older women with BC referred annually to medical and radiation oncology at the Louise Temerty Breast Cancer Clinic and the Odette Cancer Centre . The investigators will recruit consecutively seen eligible patients before radiotherapy. Experienced clinical trial staff will identify eligible patients from the clinic list of each medical and radiation oncologist, who will then introduce the study during the visit. The Research Coordinator (RC) will meet with interested patients for consent to conduct the screening assessment for signs of cognitive impairment using the Memory Impairment Screen (MIS), a sensitive and reliable tool. The MIS will take no more than 5 minutes and will be conducted in a private room at either the Louise Temerty Breast Cancer Centre or the Odette Cancer Centre depending on the location of the patient's appointment. The RC will then obtain consent from all those who pass the MIS to participate in the study and arrange for testing. The RC will administer the assessment battery at a time convenient to the patient, before radiotherapy. Drug adherence rates will be obtained using monthly telephone self-reports. After 1 year, participants will undergo the same testing protocol as at baseline using alternate forms where possible. The RC will document how many continue to meet study criteria including changes in health status, medications, etc. The investigators do not expect any major selection biases between our groups. While exclusion of women co-administered chemotherapy due to its confounding effects on cognition may bias the sample by including more women with co-morbidities, this potential bias should be reduced by our exclusion of previous cancers, life expectancy \<2 years, and central nervous system (CNS) disorders. To determine bias in attrition of women at year 1 due to cognitive impairment, the investigators will contact all participants and caregivers who do not return to determine the reason.