Table 1.

Summary of missing data for incident female stages 1–3 invasive breast cancer reported to the California Cancer Registry 2000–2010 with complete data for age, SES, year of diagnosis, survival time, and race/ethnicity (N = 179,143)

Missing	n(%)
ER	16,247 (9.0%)
PR	21,306 (11.8%)
HER2*	45,021 (24.9%)
Tumor grade	10,594 (5.9%)
Unknown cause of death	2,386 (1.5%)
Total cases with one or more of the above variables missing†	57,695 (31.9%)
Total cases with complete data	123,395 (68.1%)

^*HER2 data not easily retrievable in the registry until 2006.

^†Cases may be missing data for more than one variable.