TGFB1 and breast cancer: Our retrospective analysis focused on lymph node-negative, early-stage breast cancer patients does not indicate that the increased IBTR or any recurrence risk observed in the pSMAD2 medium patient group is due to differential effects of adjuvant RT based on TGF-β signaling in the primary tumor, as proven by the consistent and significant efficacy of RT across all pSMAD2 patient groups, with a non-significant formal interaction test between pSMAD2 group and RT.