Personality and Coming to Terms with Cancer: A Cross-Sectional Study of Five-Factor Traits and Illness Acceptance in Oncology Outpatients

Background/Objectives: A cancer diagnosis forces a rapid, often unwelcome reorganization of a patient’s sense of self, routines, and future plans, and patients vary considerably in how far they progress toward accepting that new reality. Personality is a candidate explanation for this variability, and although the Five-Factor Model has been linked to cancer-related distress and coping in several large cohorts, its relationship to illness acceptance specifically, alongside disease duration, treatment self-assessment, and perceived social support, has not been jointly examined in a single, diagnostically broad oncology sample. Methods: We surveyed 114 outpatients with a confirmed malignant tumor diagnosis, combining a study-specific questionnaire with the NEO-Five-Factor Inventory (NEO-FFI) and the Acceptance of Illness Scale (AIS). Because several study variables were non-normally distributed and the study-specific measures were ordinal, associations were examined using Spearman’s correlation, the Kruskal–Wallis H test, and the Mann–Whitney U test. Results: Illness acceptance was moderate on average (mean [M] = 26.55, standard deviation [SD] = 7.34); 22 patients (19.30%) were classified as having low acceptance, 76 (66.67%) as average acceptance, and 16 (14.04%) as high acceptance. All five personality domains correlated with acceptance, led by a strong negative association with neuroticism (ρ = −0.632, p < 0.001) and moderate positive associations with extraversion, agreeableness, conscientiousness, and openness to experience (all p < 0.001). Longer disease duration and a more favorable self-rated treatment outcome were both associated with higher acceptance, and patients who felt supported by close relatives scored higher than those who found support difficult to gauge. Conclusions: Personality traits, particularly neuroticism, were associated with illness acceptance. Brief psychosocial assessment may help identify patients reporting greater difficulties in psychological adjustment to cancer.