Normalized breast cancer survival outcomes in U.S. tumor registries.

[BACKGROUND] This study normalized the National Cancer Database (NCDB) and Surveillance, Epidemiology, End Results Program (SEER) populations to mirror the USCS population and examined survival outcomes in breast cancer following normalization.

[METHODS] Patients diagnosed with stage I-IV breast cancer (2010-2018) were selected from the NCDB and SEER. Rates obtained from the USCS were used to normalize the NCDB and SEER cohorts, using patient weighted frequencies for variables (age, sex, race/ethnicity, etc). Overall survival was estimated using the Kaplan-Meier method before and after normalization.

[RESULTS] The USCS included 2473,739 patients, the NCDB 1441,556, and SEER 504,938. There were minimal differences between the cohorts based on age or sex. There were notable differences in the racial/ethnic composition (Hispanic: USCS 8.3 %, NCDB 5.9 %, SEER 11.7 %; p < 0.001). There were minimal differences in tumor biomarkers, but significant differences in extent of disease (local: USCS 66.1 %, NCDB 80.2 %, SEER 68.4 %; distant: USCS 6 %, NCDB 3.9 %, SEER 3.9 %; p < 0.001). Variables that were similar without weighting (age, sex, tumor biomarkers), had similar OS after weighting. However, when the NCDB and SEER were weighted by stage, HR status and race/ethnicity combined, slight changes were seen in 5-year OS (NCDB regional: unweighted 76.8 % vs weighted 77.0 %, SEER regional: unweighted 79.7 % vs weighted 78.5 %; p < 0.001).

[CONCLUSIONS] US tumor registries provide data for a large sampling of breast cancer patients. Despite significant differences in case coverage based on race/ethnicity and stage, OS remained similar following normalization to the USCS, suggesting that analyses using these data sets may be generalizable to the population.