Do your radiation treatment recommendations change if a breast cancer patient does not complete a full course of neoadjuvant chemotherapy?

No. For the usual patient who has operable/resectable breast cancer, who is planned to have induction chemo followed by surgery, failure to complete the induction chemo would not alter my planned RT. Inherent to this question is the related question of: "Should we alter the RT plans based on the response to pre-operative chemo?". I personally answer this question also with a "no." My two "nos" are consistent; i.e., if I would not alter my RT based on the response to chemo, I would not alter my RT based on the amount of chemo received.

The ability to alter RT based on the response to chemo is being asked in B51 (see Mamounas et al., JCO 2019).

Pending the results of this trial, I think the standard is to deliver local-regional RT based on ...

Agree with Dr. @Dr. First Last. We continue to base radiation dose/volume/design currently on pre-chemotherapy staging (including PET, axillary imaging, and often MRI) regardless of completion of NaC. There is clearly an interest in the de-escalation of RT, which ongoing trials will help address. HERO trial is also ongoing through SWOG/NRG-BR008 looking at potential omission of RT in low risk HER2+ breast cancer patients following BCT.