If these lymph nodes do not show evidence of spread of the cancer, only the breast is usually treated with radiation. If these nodes do show evidence of cancer spread, your doctor may advise either radiation to the immediate lymph node containing areas above the breast or chemotherapy in addition to radiation treatment. They are totally different. Like surgery, radiation therapy is called a localized treatment. In radiation therapy, a specialist called a radiation oncologist directs treatment to specific areas - the area where the cancer started, the breast, and, possibly, surrounding tissue.
Chemotherapy involves the use of chemical or hormonal agents that act throughout the body.
This type of treatment is usually called systemic.