Is post mastectomy radiation therapy indicated based only on pre chemo MRI and PET CT positive axillary lymphadenopathy, if surgery following neoadjuvant chemo showed CR ?  

These patients are eligible for NRG-B51 to try to attempt to address this issue. My view on the trial is that observation is the experimental arm and radiation is the standard arm, so off trial I generally would offer post-mastectomy radiation, though there is room for flexibility depending on other...