These findings were validated by another NCDB study by Cao et al. where T1aN0 HER2 + BC patients who received locoregional therapy alone (n = 4026) were propensity-matched 1:1 to those who received the addition of systemic therapy (n = 4922), with the result demonstrating no significant improvement in OS with systemic therapy versus locoregional therapy alone (HR 1.613, P = 0.107)18. The gene discussed is ERBB2; the disease is breast cancer.