In patients with 0-1 risk factors that have a low risk of having any positive NSLNs, clinicians may be able to determine that ALND is not warranted and that axillary RT at the I-II level is sufficient to reduce the risk of regional recurrence in light of this risk and other factors including patient age, tumor size, histologic grade, ER status, and PR status [32]. This evidence concerns the gene ESR1 and neoplasm.