In women with locally advanced HER2+ breast cancer who have had a complete response to neoadjuvant chemotherapy, what factors impact your decision to offer PMRT?

Currently, the use of PMRT should be based on pre treatment staging. If pretreatment staging is stage III, I would recommend RT. If pretreatment nodal staging is IIB would favor observation but would also consider for B51 study randomizing between RT vs observation.

For my practice, any node positive patients (even T2N1) eligible for B51 would be offered enrollment. Off-protocol I would treat.

Any patient with up-front cT4 or cN2+ disease (not eligible for B51) gets PMRT.

cT3N0 prior to chemotherapy would be an individualized discussion with the patient but would favor observation with pCR.

cT1-2N0 Her2+ disease (where we are still seeing a fair amount of NAC), I would not offer PMRT.