Radioimmunotherapy (RIT) is a targeted treatment that delivers radiation therapy through a technique similar to chemotherapy. 

In RIT, a tumor-killing dose of a radioactive substance is linked to an antibody that binds directly to the cancerous cells of the tumor. The radiation kills the targeted cancer cells, while normal tissue is only exposed to a minimal dose.

The "tagged" antibodies may be injected directly into an artery, under the skin or directly into a body cavity such as the uterus. One advantage of this method is that it may be used to treat cancer that has spread and is not visible by diagnostic means. This helps eliminate the spread of the disease. RIT may also help reduce the frequency and duration of cancer treatments.