Would you offer partial breast irradiation for women with G2 4cm DCIS with close margins of 1mm but a very large breast size?

Although size cut off is arbitrary, DCIS tumor size is one of the risk factors for IBTR. For large-volume DCIS like this case in question, what is not known is if a 1 to 1.5 cm CTV margin would capture all microscopic areas of disease or do we need to treat larger volumes. For that reason, I favor I...