Abstract Background: The increasing of breast cancer survivors (BCS) as the result of treatment success involves patients demanding cares related to the adverse events of cancer treatment. Furthermore, the study of the course of the disease process and treatment over time has been a yielding perspective to understand cancer patients. Few studies have attempted to analyze changes over time since diagnosis (TSD) in women who remain disease free and are taking endocrine therapy (TET). It is known that some BCS reported high levels of quality of life (QoL), no changes in social support (SS) and that survivors without chemotherapy as adjuvant treatment had better QoL that those who had received it. However, the changes over time in terms of unmet needs (UN), QoL, and perceived SS outcomes in Mexican BCS have no examined, which is fundamental to identify convenient goals, better times of integrated interventions and optimize our human resources according to the trajectory of cancer treatment. Objective: Identify changes over TSD, and the time TET in terms of UN, SS perception and QoL on Mexican BCS. Method: 368 patients with BC and TET were enrolled in a cross-sectional and comparative design, were assessed using QoL (EORTC-30 and BR-23), UN (SCNS-SF32), SS (MOS-SSS14), validated and standardized instruments in a Mexican cancer population. Premenopausal patients with ovarian function suppression were excluded. Patients were divided into four groups according to TSD and time TET, both in ≤1year and >1year. Parametric and non-parametric analyses were used: t Student and U Mann Whitney. Results: Patients mean age was 54 (SD=10.6) years; mean of TSD was 38 (SD=24) months, and they had 30 months on average (SD= 19) TET. The level of global QoL was high (78%) as well as the level of SS (73%), the UN were low (28%). Cognitive function was the most rated concern in terms of QoL for all groups. “Help with daily shores" was the type of SS, which all groups perceived the lowest support. "Fear about cancer spreading" and “Concern about worries of those close to you” were the first and second rated UN in all groups. Additionally, we found that patients with ≤1year of TSD had more significantly insomnia, financial difficulties, psychological and global UN (p=.02; p=.01; p=.0005; p=.01, respectively) than patients with >1 year of TSD. Moreover, the results showed that after one year of time TET: psychological and global needs, besides tangible and global SS, diminished significantly (p=.002; p=.009; p=.01; p=.03, respectively), nevertheless, the future perspective of health increases significantly (p=.01). Discussion and conclusions: Our findings are consistent with previous studies in terms of QoL. These results indicate that not only BCS patients improve physically, but also psychosocially over time: they are more independent, also have a better perspective of their health even though the fear persists. In conclusion, all biopsychosocial aspects evaluated improve over time. These data suggest that the most optimal effort might be provided to newly diagnosed patients, which is fundamental information for a country as Mexico with a lack of human resources. For instance, health staff could be focused on providing tools to deal with fears, social concerns, and physical/cognitive symptoms as a priority in this vulnerable group. Citation Format: Lizette Gálvez-Hernández, V Neri-Flores, I Paéz-Gerardo, E López-Muñiz, I Monroy-Ortiz, A Mohar-Betancourt, Enrique Bargallo-Rocha, Cynthia Villarreal-Garza, Paula Cabrera-Galeana. Biopsychosocial changes since diagnosis and the time taking endocrine therapy in Mexican patients with breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-13-08.