TPS9148 Background: Breast cancer patients might develop impaired sleep patterns during chemotherapy, and impaired cognitive function has been associated with sleep patterns disruption. It has been suggested that sleepiness (sleep tendency) in cancer patients is prevalent and causes distress in the patient’s quality of life, that and their cognitive abilities are also affected. Furthermore, increased blood glucose levels among women undergoing chemotherapy may contrubute to memory deficits in breast cancer patients. It is proposed that Prospective and Working Memory are being affected by the disturbance of these biological factors over the course of chemotherapy. Methods: Ninety participants will be invited to take part in the study. Thirty will be breast cancer patients receiving chemotherapy treatment, thirty breast cancer patients receiving treatment other than chemotheray, and thirty healthy controls. Measures of sleep and sleepiness, will be administered at 4 testing sessions during a 9-month period, along with a neuropsychological battery. Additionally, blood samples will be analysed. Eight of planned 60 cancer patients have been enrolled, and four of them have completed the second testing session. For the assessment of sleep/wake activity, participants will be required to wear a sleeping monitor (sensewear armband) for 7 days. Pupil dilatation to observe sleepiness will be meassured by using a Pupillometry developed at Poole hospital in the UK. Prospective Memory will be assessed using CAMPROMT test to analyse if this is a more sensitive measure for mild cognitive impairment. Discussion: Impairment on variables such as sleep, sleepiness and glucose have not been studied within the context of Chemo-Brain on breast cancer patients.Therefore we want to observe whether impaired sleep and sleepiness, and impaired glucose levels are at the core of Prospective and Working Memory decline in Chemo-Brain patients in order to find a cause-and-effect relationship as a consequence of chemotherapy.