Adjuvant therapy is often used after primary treatments, such as surgery, to lessen the chance of your cancer coming back. Even if your surgery was successful at removing all visible cancer, microscopic bits of cancer sometimes remain and are undetectable with current methods. Adjuvant therapy given before the main treatment is called neoadjuvant therapy. This type of adjuvant therapy can also decrease the chance of the cancer coming back, and it's often used to make the primary treatment — such as an operation or radiation treatment — easier or more effective. Adjuvant or neoadjuvant therapy can cause significant side effects, and these treatments don't benefit everyone.