BACKGROUND: This study compared incident breast cancer cases in the National Cancer Database (NCDB) and Surveillance, Epidemiology, End Results Program (SEER) to a national population cancer registry. METHODS: Patients with malignant or in situ breast cancer (BC) 2010-2019 in the NCDB and SEER were compared to the US Cancer Statistics (USCS). Case coverage was estimated as the number of patients in the NCDB/SEER as a proportion of USCS cases. RESULTS: The USCS reported 3,047,509 patients
77.5% patients were included in the NCDB and 46.0% in SEER. Case ascertainment varied significantly by patient sex (both registries, p <
.001). For males, 84.1% were captured in the NCDB, whereas only 77.5% of females were included. Case coverage in SEER was better for females than males (46.1% vs. 43.5%). Registries varied significantly by race/ethnicity (both p <
.001). Case coverage in the NCDB was highest for non-Hispanic White (78.2%), non-Hispanic Black (77.7%), and non-Hispanic Asian or Pacific Islander (72.5%) BC patients, and lowest for Hispanic (56.4%) and non-Hispanic American Indian/Alaska Native (41.1%) patients. In SEER, case coverage was highest for non-Hispanic Asian or Pacific Islander (78.1%) and Hispanic (69.6%) patients and it was significantly lower for all other subgroups (non-Hispanic Black, 44.8%
non-Hispanic White, 42.4%
and non-Hispanic American Indian/Alaska Native, 36.6%). CONCLUSIONS: National US tumor registries provide data for a large sampling of breast cancer patients, yet significant differences in case coverage were observed based on age, sex, and race/ethnicity. These findings suggest that analyses using these data sets and interpretation of findings should account for these meaningful variances.