What is the appropriate timeline to start post mastectomy chest wall/regional nodal XRT (+/- reconstruction) after surgery?

If the patient received neoadjuvant chemotherapy, we typically give RT prior to additional chemotherapy (ex. xeloda for triple negative with residual, TDM1 for HER2+ with residual) and try to start 4-6 weeks post-op given that they are well healed and/or reconstruction/expanders completely filled. I...