Validity of self-reported breast cancer characteristics in a nationwide cohort of women with a family history of breast cancer

Background: Women may have incomplete understanding of a breast cancer diagnosis, leading to inaccurate reporting in epidemiological studies. However, it is not feasible to obtain consent for medical records from all women participating in a study. Therefore, it is important to determine how well self-reported breast cancer characteristics correspond with what is found in medical records, but few studies have evaluated agreement of self-reported breast cancer characteristics with abstracted medical records. Methods: We calculated the positive predictive value (PPV) of self-reports compared to medical records and explored whether participant characteristics may have influenced reporting accuracy. We analyzed data from 2518 reported breast cancer cases from the Sister Study, a large nationwide cohort of women with a family history of breast cancer. Results: Medical records or pathology reports were obtained for 2066 of 2518 (82%) women who reported incident breast cancer. Breast cancer was confirmed for over 99% (n = 2054) of women with medical records. Confirmation rates were high for invasive, ductal, hormone receptor positive, and HER2 negative breast cancers, with little variation by race/ethnicity or age. Self-reported in situ breast cancer had a lower PPV (64.2%), with medical records showing invasive breast cancer instead, especially for older and Hispanic women. Hormone receptor (ER and PR) negative and HER2 positive self-reports had lower PPVs (83.0%, 71.6%, and 66.1% respectively). Hispanic women and women ages 65 or older at diagnosis were less able to accurately report breast cancer stage, excluding stage I. Conclusions: Accuracy of reporting overall breast cancer and common subtypes is high. Despite having a family history of breast cancer and voluntarily enrolling in a study evaluating breast cancer risk factors, participants may have greater difficulty distinguishing between in situ and invasive breast cancer and may less accurately report other less common subtypes. Discrepancies may reflect women's poor understanding of information conveyed by health care providers or lack of consistent terminology used to describe subtypes.