Dear kmom, The use of radiation therapy is to try to prevent local recurrence (cancer coming back at the original site). When planning the radiation therapy all attempts are made to target the area of greatest concern for possible recurrence while protecting normal areas. If it can be, radiation therapy to the axillary area is generally avoided. This is because radiation to this area can increase the risk of lymphedema. The axillary lymph node spread is considered more of a systemic process which the adjuvant chemotherapy treats.
You helped me understand the reason why my doctor did not pursue axilliary node radiation. He did not give me any specific reason.