Here are the main ways radiation therapy is used to treat breast cancer:
Radiation after lumpectomy
Radiation therapy for breast cancer is almost always recommended after surgery that removes only the tumor (lumpectomy). A lumpectomy alone, without radiation therapy, carries a relatively high risk of cancer recurrence in the affected breast months or years later because of microscopic deposits of cancer left behind after surgery. Radiation helps to destroy remaining cancer cells.
Lumpectomy combined with radiation therapy is often referred to as breast-conservation therapy. In clinical trials comparing lumpectomy with and without radiation therapy, the addition of radiation therapy after a lumpectomy resulted in significantly decreased rates of breast cancer recurrence and proved to be as effective as having the entire breast removed.
Radiation after mastectomy
Removal of the entire breast (mastectomy) usually means you won't need radiation therapy. But radiation therapy is sometimes recommended for women at high risk of cancer recurrence. Factors that may put you at high risk of breast cancer recurrence in your chest wall include:
- Lymph nodes with signs of breast cancer. Underarm (axillary) lymph nodes that test positive for cancer cells are an indication that some cancer cells have spread from the primary tumor. The more positive nodes you have, the more likely your doctor is to recommend radiation therapy. Experts agree that having four or more positive nodes is a clear indication for radiation therapy after mastectomy, although data suggest that even women with fewer positive lymph nodes may benefit from radiation therapy.
- Large tumor size. A tumor greater than 5 centimeters (about 2 inches) generally carries a higher risk of recurrence than do smaller tumors.
- Tissue margins with signs of breast cancer. After breast tissue is removed, the margins of the tissue are examined for signs of cancer cells. Very narrow margins or margins that test positive for cancer cells are a risk factor for recurrence.
Radiation for locally advanced breast cancer
Radiation therapy can also be used to treat:
- Breast tumors that cannot be surgically removed.
- Inflammatory breast cancer, an aggressive type of breast cancer that spreads to the lymph channels of the skin covering the breast. People who have this type of breast cancer typically receive chemotherapy before a mastectomy, followed by radiation, to decrease the chance of recurrence.
Radiation for managing metastatic complications
If breast cancer has spread to other parts of your body (metastasized) and a tumor is causing pain or some other symptom, radiation can be used to shrink the tumor and ease that symptom.