Objective: Identify which variables are predictors of treatment adherence in cancer patients.Methods: Two hundred twenty cancer outpatients were evaluated by the following instruments: questionnaire on sociodemographic and clinical data, NEO-FFI Personality Inventory Revised (NEO-FFI-R), Multidimensional Health Locus of Control (MHLC) scale, Hospital Anxiety and Depression Scale (HADS), patient's knowledge about cancer disease questionnaire, and Adherence Determinants Questionnaire (ADQ). A logistic regression analysis was applied to verify the predictive power of the variables, and network analyses were conducted through the qgraph package.
Results:The sample was composed of 138 (62.7%) women and 82 (37.3%) men.The mean age of participants was 54.66 (SD = 13.30), and the education level mean was 8.32 (DP = 3.76) years of study. Powerful others locus of control (LOC) and the personality factors conscientiousness and agreeableness are presented as predictors of high treatment adherence. The variable family cancer history, on the other hand, was a predictor of lower adherence levels. Conclusions: The powerful others LOC may be connected with more trust and dependence in the health team, leading to better adherence. Specific characteristics of personality factors can help individuals to cooperate with their caregivers and to follow medical orders. The evaluated factors are interrelated and should be taken into account by health professionals when developing interventions to modify healthrelated behaviors and treatment adherence. KEYWORDS agreeableness, cancer, conscientiousness, locus of control, oncology, treatment adherence 1 | BACKGROUND Adherence of treatment can be defined as a rigorous following of health professional's recommendations, which include orientations about medicines, lifestyle changes, and preventive measures. The adherence is an attitude and a behavior: like attitude, it implies a willingness to follow the prescription recommendations; as a behavior, it is associated with the attainment of specific orientations. 1The concept is not related only to patients taking medication or not. Besides that, it is related to how a patient administers his/her own treatment, behavior factors, perceptions and ways of coping with adversity, and elements related to the health system that takes care of the individual. Thus, both aspects related to patient or disease/treatment can influence treatment adherence. 2 In this way, it is possible to understand that it is difficult to define which factors have major significance and how they interact when