Based on 150 T1-2N0-1a breast cancer patients, who were treated with radical mastectomy without adjuvant RT, they reported in the univariate analysis that premenopausal status (p = 0.004), presence of LVI, estrogen receptor (ER) negative (p = 0.02) and pathologic grade 3 tumour (p = 0.002) were associated with higher risk of LRR. This evidence concerns the gene ESR1 and breast cancer.