How accurately does the medical record capture maternal history of cancer?

We sought to assess the reliability of information regarding the maternal h istory of cancer by comparing the medical records of 214 women with breast cancer, ages 26-59 years and diagnosed in 1974-1995, and of their controls with the medical records of their mothers. Subjects were members of Falser Permanente, Northern California, selected for a study of early-life predict ors of breast cancer. For any type of cancer identified in the mother's med ical record, the proportion noted in the daughter's medical record at least 6 months before the daughter's diagnosis or reference date was 56% among c ases and 32% among controls. The odds ratio for the association of maternal cancer history with breast cancer risk was 2.1 using the maternal record a nd 3.5 using the subject's record. For a maternal history of breast cancer, the proportion noted in the subject's record was 79% among cases and 57% a mong controls, and the odds ratios were 4.0 and 6.5, respectively. We belie ve that the case-control difference in missing information was attributable to higher utilization of breast cancer screening among cases. This study i llustrates the need to assess the impact of screening differences on the as certainment of information from the medical records.