Is radiation needed or not….
I think the reason with the margins is that a close (or small) margin means some cancer is near the edge of the excised tissue, so could still be on the other side of the cut, still in the breast. That is what happened with me with DCIS, and a big reason I agreed to radiation.
A large margin means the area (margin) between edge of excised tissue and cancer is wider, so the cancer is well inside the excised tissue, so less chance of it being left in the breast.
~J
Please learn more about your health care! Education is key!