Would you offer ultrahypofractionated 5-fraction whole breast only for a women with ER-/HER2+/cN+ disease with pCR following neoadjuvant systemic therapy?

If the plan is to treat breast only then 26 Gy in 5 with and without boost is fine. The philosophy of treating RNI would vary based on the interpretation of 5 years of B-51 data.