Women with estrogen-negative breast cancer who received radiation after a mastectomy lowered their recurrence risk by 30 percent and increased their five-year survival by 50 percent. Those who especially benefitted from post-mastectomy radiation were younger than 40 years old; had high nuclear grade, estrogen-negative tumors status; and had cancer that had spread to their lymph nodes. This according to research published in the International Journal of Radiation Oncology.