Purpose: To investigate the effect of understanding their own disease by patients with metastatic breast cancer on their survival potential after being informed by their physician.
Patients and methods: Two hundred and fourteen women with metastatic breast cancer who participated in a multi-institutional, randomized phase III trial (Japan Clinical Oncology Group (JCOG) Study 8808) were asked whether they understood their own disease after being given information about the clinical trial. They were classified into two groups on the basis of whether they understood or not. We estimated their survival after the time of registration and derived relative hazard ratios from Cox's proportional hazards model.
Results: There were 190 patients in the 'better understanding' group and 24 in the 'poor understanding' group. Median survival times after registration were 28.3 and 16.1 months, respectively. The 'better understanding' group showed a significant difference from the 'poor understanding' group (p = 0.016). In multivariate regression analysis, patients who did not understand still showed poorer survival than those who understood (hazard ratio = 2.09; 95% confidence interval (CI) 1.16-3.78; p = 0.014).
Conclusion: These results support the supposition that patients' understanding of information about their disease may influence their survival. Thus, it is important to evaluate patients' recognition about information even after obtaining their consent. However, further investigation is needed to clarify the exact nature of this relationship.