The prognostic differences and the effect of postmastectomy radiotherapy between post-chemotherapy ypT1-2ypN1 and de novo pT1-2N1 breast cancer.

There seemed no survival difference in post-chemotherapy ypT1-2ypN1 and de novo pT1-2N1 BC patients with contemporary systemic therapy. In addition, PMRT might be exempted in patients with post-chemotherapy ypT1-2ypN1 BC, while not in patients with de novo pT1-2N1 BC.