Radiation after a mastectomy for advanced breast cancer is part of the standard treatment guidelines. But more than a decade after the lifesaving value of radiation was confirmed, about half of all women who should get radiation therapy aren't getting it, researchers reported Monday. In the mid-1990s, several studies confirmed that mastectomy patients with advanced breast cancer have better outcomes if they undergo radiation after surgery. Initially, the medical community seemed to pay attention to the findings. From 1996 and 1998, the rates of radiation following mastectomy for women ages 66 and older increased from 36.5% to 57.7%. But in a review of data from 1998 to 2005, researchers from MD Anderson Cancer Center in Houston found no further increase. Almost half of all eligible women are not getting radiation therapy. The study appears online in the journal Cancer.