RESUMO
BACKGROUND: Stress and depression were reported as negative prognostic factors in breast cancer patients and monoamine oxidase (MAO) activity was considered a marker of mental suffering. MATERIALS AND METHODS: MAO activity in platelets was determined in a group of newly diagnosed breast cancer patients, after the communication of diagnosis and surgery, using the Mental Adjustment to Cancer (MAC) and Hospital Anxiety and Depression scales (HADS). RESULTS: The analysis of regression indicated that hopelessness-helplessness positively correlated with depression, anxiety and anxious preoccupation. Monoamine oxidase (MAO) activity displayed a positive regression coefficient with depression score. At follow-up, Cox analysis of survival indicated that MAO activity was a marginally significant risk factor. CONCLUSION: Further research in a larger group of patients may support the present results, showing that MAO activity is a biological marker of difficulties in mental adaptation to cancer and is a risk factor for survival.