Is Radiation Therapy Required After Double Mastectomy?

I have had a double mastecomy, where they removed 4 tumors from my right breast (all four tumors totaled less then 4 cm). I'm 49 years old and have completed 4 treatments of chemotherapy. All the tumors were completely taken (no margins) and it was microscopically found in my first lymph node. Is radiation required now for my chest wall?