The Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute is an authoritative source of cancer incidence and survival statistics that covers about 30% of the United States population.35 In an initial SEER analysis that included 4691 patients with HR+, HER2-negative, N+ breast cancer (defined as micrometastases and 1–3N+) who had RS results, the 5-year estimates of BCSM were significantly different by RS group (p < 0.001): 1.0% with RS <18, 2.3% with RS 18–30, and 14.3% with RS ≥31 (Table 3). Here, ERBB2 is linked to cancer.