Local radiation therapy for breast cancer, which treats the area where the cancer was found, doesn’t usually make a major impact on the immune system. Radiation treatments can irritate the skin, causing small breaks that could allow bacteria and germs to enter. Talk to your doctor about how best to care for your skin. For more information, visit the Managing Skin Side Effects page in the Radiation Therapy section.
If you have radiation therapy to the underarm area, where lymph nodes are, there can be some scar tissue formation that damages the lymph nodes and vessels. This can contribute to a longer-term risk of infection in the arm, hand, and upper body, especially if you also had lymph nodes removed. Infection in these areas can lead to a condition called lymphedema, in which lymph fluid collects in the hand, arm, or other area, causing swelling and pain. Read more about ways to reduce the risk of lymphedema.
Radiation is more likely to weaken your immune system if it’s directed at the bones, especially the bones in your pelvis, where the marrow functions as a blood cell factory. Some women with metastatic breast cancer need to have this type of radiation. With bone radiation, the effect on the immune system can be similar to that of chemotherapy. In this situation, you could experience a low white blood cell count and even neutropenia. Your doctor may order complete blood cell counts to check on your white blood cells levels. If levels are too low, he or she may need to adjust your treatment and/or prescribe medications that stimulate white blood cell production.