Early breast cancer is considered invasive when the cancer has grown beyond the milk ducts or lobules of the breast where it first started. Non-invasive breast cancer is usually called "in-situ" cancer—ductal or lobular carcinoma-in-situ (DCIS, LCIS). In addition to surgery, most women with early, invasive breast cancer will also receive radiation therapy and often some form of chemotherapy. The radiation therapy may be followed by chemotherapy, or chemotherapy may be given first—sometimes even before surgery. Chemotherapy and radiation therapy are used in this way to lower the risk of the cancer ever coming back after surgery (recurrence).
A study tried to answer the question of whether giving the radiation and chemotherapy at the same time (simultaneous therapy) would be better than giving them at different times (sequential therapy).
The researchers found that ten years later, women who received radiation and chemotherapy at the same time were less likely to have their breast cancer come back. 92% of women who received radiation and chemotherapy at the same time remained breast cancer free ten years later. Only 83% of women who received the two forms of treatment at different times remained free of breast cancer. That lowered risk of breast cancer recurrence came at some price, in the form of more side effects during treatment.
Most cancer specialists today give radiation and chemotherapy in sequence. That will probably remain the "standard" until more information about simultaneous therapy is available. If you have recently been diagnosed with early, invasive breast cancer and your doctors are considering both radiation and chemotherapy around the time of your surgery you can talk to them about the timing of those treatments and the results of the research reported here.