Nonparticipants in the past screening were more likely to have larger tumors (adjusted odds ratio [AOR], 1.55 [95% CI, 1.37-1.76] for a tumor size ≥20 mm), lymph node involvement (AOR, 1.28 [95% CI, 1.12-1.45), and distant metastasis (AOR, 4.64 [95% CI, 2.10-10.29]) and less likely to have estrogen receptor–negative breast cancer (AOR, 0.74 [95% CI, 0.60-0.92]); however, there were no differences in progesterone receptor status (AOR, 0.96 [95% CI, 0.83-1.11]) or ERBB2 (formerly HER2 or HER2/neu) status (AOR, 1.00 [95% CI, 0.81-1.24]). The gene discussed is ERBB2; the disease is breast cancer.