Reliability of Self-reported Treatment Data by Patients With Breast Cancer Compared With Medical Record Data

Medical records are considered the gold standard for accurate treatment information. However, treatment data are increasingly obtained from questionnaires. It can be questioned whether self-reported treatment data are reliable, particularly because patients have to process a lot of information during their diagnosis and treatment process. The present study assesses the reliability of self-reported treatment data compared with medical records.

All patients with stage I, II, and III breast cancer (n = 606) in 5 hospitals in the west of the Netherlands were invited to complete a questionnaire 9 to 18 months after surgery. We calculated kappa statistics, proportion correct, sensitivity, specificity, and positive and negative predictive values to assess agreement.

Three hundred fifty patients completed the questionnaire (58%). Agreement was good for type of surgery and receiving chemotherapy, endocrine therapy, and radiation therapy, with sensitivity and specificity of 95% or higher and kappa above 0.90. However, only moderate agreement was seen for sentinel node biopsy, including the pathologic results and axillary lymph node dissection (kappa between 0.60 and 0.80). Lack of agreement was more often found for patients who had received endocrine therapy (odds ratio, 1.85; 95% confidence interval, 1.11-3.10) but not influenced by age (odds ratio, 1.00; 95% confidence interval, 0.98-1.02).

Accuracy of self-reported data is high for type of surgery, chemotherapy, endocrine therapy, and radiation therapy, but much lower for sentinel node biopsy including the pathologic results and axillary lymph node dissection. This is relevant for clinicians given the time spent explaining these procedures, and for researchers to help decide what information to obtain from patients or medical records.