Background: Breast cancer continues to be the most commonly diagnosed cancer in women. Breast cancer survivors face numerous problems, especially after completing the first year of intense treatment. We present the protocol for an ongoing study to analyze the impact of a series of factors on breast cancer survival related to lifestyle, emotional well-being, and use of complementary and alternative medicine (CAM). Objective: We aim to analyze the influence of social determinants, lifestyle changes, emotional well-being, and use of CAM in the progression of breast cancer in women diagnosed with breast cancer between 2003 and 2013 in Barcelona, Spain. Methods: We will perform a mixed cohort study (prospective and retrospective) of women diagnosed with breast cancer, created using a convenience sample in which we study the evolution of the disease (relapse, death, or remaining disease-free). Once identified, we sent the women information about the study and an informed consent form that they are required to sign in order to participate; a total of 2235 women were recruited. We obtained the following information from all participants: sociodemographic profile via a phone interview, and a self-administered survey of information about the study's objectives (lifestyles, emotional well-being, health care services, and the use of CAM). Lastly, we examined clinical records to obtain data on the tumor at the time of diagnosis, the treatment received, the occurrence of relapses (if any), and the tumor typology. We present data on the women's social profile based on descriptive data obtained from the telephone interview (welcome survey). Results: Based on the welcome survey, which was completed by 2712 women, 14.42% (391/2712) of respondents were <50 years of age, 45.50% (1234/2712) were between 50 and 65 years of age, and 40.08% (1087/2712) were >65 years of age. A total of 43.69% (1185/2712) belonged to the highest social classes (I and II), 31.27% (848/2712) to the middle class (III), and 23.49% (637/2712) to the working classes (IV and V). Approximately 22.71% (616/2712) lived alone, 38.31% (1039/2712) lived with one person, and 38.97% (1057/2712) lived with two or more people. Conclusions: We obtained information from a large cohort of women, but this study has limitations related to the convenience sampling strategy, one of which is reduced representativeness. Conversely, being a self-administered survey, the study introduces biases, especially from respondents that answered on paper. However, the information that the study provides will serve as the basis for designing future interventions aimed at improving the knowledge gaps indicated for women with breast cancer.