Abstract Background: A care pathway is defined as patient-focused global care that addresses temporal (effective and coordinated management throughout the illness) and spatial issues (treatment is provided near the health territory in or around the patient's home). Heterogeneity of the care pathways in breast cancer (BC) is presumed but not well evaluated. The OPTISOINS01 study aims to assess every aspect of the care pathway for early BC patients using a temporal and spatial scope. Trial design: An observational, prospective, multicenter study in a regional health territory (Ile-de-France, France) in different types of structures: university or local hospitals and comprehensive cancer centers. The study consists of three work-packages: - Cost of pathway The aim of this WP is to calculate the overall costs of the early BC pathway at one year from different perspectives (society, health insurance and patient) using a cost-of-illness analysis. Using a bottom-up method, we will assess direct costs, including medical direct costs and nonmedical direct costs (transportation, home modifications, home care services, and social services), and indirect costs (loss of production). - Patient satisfaction and work reintegration Three questionnaires will assess the patients' satisfaction and possible return to work: the occupational questionnaire for employed women; the questionnaire on the need for supportive care, SCNS-SF34 ('breast cancer' module, SCNS-BR8); and the OUTPASSAT-35 questionnaire. - Quality, coordination and access to innovation Quality will be evaluated based on visits and treatment within a set period, whether the setting offers a multidisciplinary consultative framework, the management by nurse coordinators, the use of a personalized care plan, the provision of information via documents about treatments and the provision of supportive care. The coordination between structures and caregivers will be evaluated at several levels. Day surgery, home hospitalization and one-stop breast clinic visits will be recorded to assess the patient's access to innovation. Inclusion criteria: Histologically confirmed, previously untreated, operable breast cancer women; residence in the Yvelines, Hauts-de-Seine or Val d'Oise departments, Ile-de-France, France. Exclusion criteria: previous history of breast cancer; metastatic, locally advanced, or inflammatory breast cancer, as defined by the AJCC (7th Edition); unstable over the following 12 months. Statistical methods: Homogeneous groups of patients will be established based on the patients' individual medical information, and care pathways will be compared. The endpoints are the costs of care pathways, patients' satisfaction, work reintegration, readmissions and time lapses between care stages. A multiple correspondence analysis will be conducted with care resource use and socio-demographic and medical characteristics as active variables. The variables that constitute the endpoints will be projected onto a space defined by appropriate axes. Present accrual and target accrual: 307 patients have been included on 800 scheduled. Citation Format: Lerebours F, Héquet D, Baffert S, Hoang HL, Brédart A, Asselain B, Alran S, Berseneff H, Huchon C, Trichot C, Combes A, Alves K, Koskas M, Nguyen T, Roulot A, Rouzier R. Optisoins01: Optimizing the patient-breast cancer care pathway; An observational multicentric prospective study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT2-04-01.