According to Carolyn M. Kaelin M.D., M.P.H, author of "Living Through Breast Cancer" who is a breast cancer survivior herself says to be very careful with upper body exercises and to never spend an entire strength-training session only on your arms. If fact, she recommended only 10 reps per set. She says that a gradual, progessive strength-training program is the safest. If you are having arm swelling, I would definately get to the doctor for advice.
Best of luck,
Linda Lou