You state the issues well. The NCCN guideline is to "consider" omission of irradiation for locoregional treatment for patients 70 or older with early stage negative node invasive breast cancer after breast conserving surgery (not mastectomy) who receive endocrine adjuvant therapy. It seemed to me that the dropping of radiation is based on mortality from metastatic spread, and, as you say, on lessening harmful medical treatment where advisable. But my questions are--what if the patient can't tolerate an aromatase inhibitor, and would such an omission incur greater risk of locoregional recurrence that would lead to more surgery and even radiation at a later age when it would be harder to endure? Like you, I have read research on this subject that discusses costs, which I find objectionable and ageist. As always, it is up to the individual woman to weigh benefit and risk and feel comfortable with those choices. Good discussion!