ERBB2 and breast cancer: This cohort study is, to our knowledge, the first to use the NCDB in over 1 million patients diagnosed with ERBB2-low or ERBB2-negative breast cancer and reflects the geographic and ethnic distribution typically seen in the disease within the US.22 Similar to prior studies,10,11 we found that ERBB2-low status is more frequent in hormone receptor–positive than triple-negative disease.