Abstract Background: Cognitive complaints (“chemo brain”) are reported frequently after breast cancer treatment but little is known about its incidence and causes. Before we can intervene we need to be able to diagnose it properly. Mini Mental state examination (MMSE) can detect advanced Alzheimer's but won't help in detecting mild cognitive disturbances. We used Montreal Cognitive Assessment for Telephone (MoCA-T) and full scale Montreal Cognitive Assessment for Telephone (MoCA) to diagnose mild cognitive impairments in patients having normal MMSE. Methods: 20 breast cancer survivors aged 50 years or older completed MoCA-T and MoCA, a year after they completed their treatment for breast cancer, describing the impact of their treatment regimen on their short term memory and ability to think and concentrate. On Day 5, they underwent a standardized laboratory protocol that assessed both behavioral and electroencephalographic (EEG) indicators of memory consolidation. Results: Patient characteristics: 20 postmenopausal breast cancer survivors aged 50 or above participated in the study a year after they completed their therapy. We are reporting preliminary results of 10 patients. Patients had stage I-III disease (stage I – One patient, Stage II – five patients, and stage III- four patients). All of them received various chemo regimens e.g. Cytoxan, methotrexate, 5-FU (CMF), Taxol, Trastuzumab (TH), Adriamycin (AC), taxotere, carboplatin (TCH). 8/10 patients received adjuvant radiation. 1/10 patient underwent reconstruction later. 7/10 patients received hormonal therapy with aromatase inhibitors. Results of MoCA –T and MoCA: MoCA-T, tests attention and concentration, executive functions, memory, language, conceptual thinking, calculations, and orientation. Possible scores range from 0-22 and scores <18 indicate mild cognitive impairment. The MoCA has possible scores from 0-30 and a score >26 is normal but <19 is indicative of cognitive impairment. 5/10 patients had abnormal MoCA and 3/10 patients had impaired MoCA-T signifying that almost 50%patients develop mild cognitive impairment after breast cancer treatment. During memory consolidation, EEG contained less theta and frequent bursts of alpha waves which is commonly seen in patients with neuropathic pain and insomnia. MoCA-T and MoCA results for the patientsPatient no.MoCA-TMoCAPtient 00817*23*Patient 0102126Patient 0111923*Patient 01216*27Patient 0132027Patient 01517*21*Patient 0161824*Patient 0172025*Patient 0191926Patient 0202129*presents affected patient Conclusions: The study signifies that mild cognitive impairment from breast cancer treatment (or “chemo brain”) was frequently reported and MoCA-T and MoCA tests were able to show even mild cognitive impairment in these patients. We are compiling our full data for EEG but the early results show that the patients had less theta but had frequent bursts of alpha waves, a pattern seen commonly in patients with insomnia and neuropathic pain. They retain fewer items and take more time responding to items as compared to normal people. We need more studies to diagnose and treat mild cognitive impairment (“chemo brain”) in breast survivors as most of these patients are still working and can be a valuable part of the community. Citation Format: Razaq WA, Tanaka T, Carlson B, Wenger M, Friedman J, Benbrook D, Craft M. Diagnosing cognitive impairment (“chemo brain”) in breast cancer survivors [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-20-09.