Purpose: To investigate the effect of understanding their own disease by pa
tients with metastatic breast cancer on their survival potential after bein
g 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 tri
al (Japan Clinical Oncology Group (JCOG) Study 8808) were asked whether the
y understood their own disease after being given information about the clin
ical trial. They were classified into two groups on the basis of whether th
ey understood or not. We estimated their survival after the time of registr
ation and derived relative hazard ratios from Cox's proportional hazards mo
Results: There were 190 patients in the 'better understanding' group and 24
in the 'poor understanding' group. Median survival times after registratio
n 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 = 2.0
9; 95% confidence interval (CI) 1.16-3.78; p = 0.014).
Conclusion: These results support the supposition that patients' understand
ing of information about their disease may influence their survival. Thus,
it is important to evaluate patients' recognition about information even af
ter obtaining their consent. However, further investigation is needed to cl
arify the exact nature of this relationship.